89 1/2 ton to 3/4 ton swap (or 1 ton, for that matter)

Hello and Happy Fourth of July to all!

I have a project in mind and am looking for the input of some of the good people here.

I currently own a 1989 GMC C1500 (standard cab, long bed) that I just had repainted.

It's pretty much factory stock at the moment (4l60 transmission, 5.7L 350 TBI engine).  However, I have been thinking about replacing the 210hp 350 with a Ramjet 502 and the 4l60 with a heavy duty th400+Gear Vendors Overdrive (we don't have vehicle inspections anymore here so passing emissions tests won't be a problem).  But, when I got to thinking about all that power, I began thinking of what I could do with it (a nice sized travel trailer came to mind).

But, as I'm sure your guessing, even with the heavy duty engine and transmission, it is still a 1/2 ton pickup.

I put that on the back burner for a while and was reading about powder coating and really got interested in having the frame of the pickup powder coated (rust, aesthetics, etc.)  Then it came to me, if I'm thinking about having the cab and box removed (along with everything else, etc.) what if I could switch out the 1/2 ton frame with an 1989 (or other compatible year) 3/4 ton or 1 ton frame?

Basically, I'm wondering if the cab and long-bed of my current 1989 1/2 ton will attached without problem to a 1989 3/4 or 1 ton frame?

I know the frames get stiffer the more weight they are expected to carry, but are the cabs and beds different between the different models?  

I think you got a good thing going. But from what I read there is one thing wrong. In an 89 1500 the trans was a 700R4 unless you swaped it with a 4L60e and a trans control unit. But is irrelivant if you want to swap to a th400 and a gear vendors od. My oppinion would be to get a 4L80e or 85e and a trans control unit. You can get these out of any hummer or 2500 and 3500, non alicion truck. This trans would be stronger and less hassal. You might save some money and deffinetly save alot of room that the gear vendors will take up.

The frame that your wanting to put under is going to be the same if you match them up right. example. you have a standard cab, long bed then you need to get a standard cab, long bed frame. If you can't find one then get a frame that is the same length and just move the mount brackets.. Or what you can do is take you frame you have now and box the frame by welding 1/8 plate mild steel on the inside of the frame. This will save you more money and you know everything will fit.  (Make sure you secure the frame real good so the frame doesn't warp)  

you should be able to find a frame at a junk yard easy, but like said above it needs to be a regular cab (suburban and crew cab frames are longer) and wont line up without modifications. The 400THM and gear vendors is the way to go over the 4l80E. I have a 83 chevy crew cab dually with a 502HT truck crate engine. The truck weighs 6500 lbs!!! empty has a 400 thm trans it will pull anything!! I recommend this engine to anyone with a 1 ton truck!! I want to install the gearvendors unit but, I think it cost about $2,200 not in my budget yet, clearance is not an issue with a full size truck but the drive shaft has to be cut. The 4l80 cost about $3500 for a new unit with the controller and the shifter has to be tinkerd with also. I dont recommend welding on a truck frame that is gonna be hauling a lot of weight unless you know what you are doing. good luck with your project.  

I had never heard of the 502HT variant until just reading your post.  I just got through looking it up and am pretty impressed with it's towing specs (high torque at relative low RPMs, etc.)

I had planned on putting the higher powered version (510hp, 560lbs. torque) in my truck for the sportiness of it, but I'm now wondering if that's a good idea.

Is the 502HT a stronger engine for a pickup over the standard Ramjet 502, or is the HT just meant for maximum pulling power at lower speeds?  

It is not going to be any stronger, It is built to pull a heavy load constantly. I have never pulled any thing with a 500+hp engine but I bet you could never keep it cool especially if it is above 90 degrees with the air on. The 502HT will run on 89 octane. With it in my truck and 3.73 dana 70 rear and 400 trans the rpm@55 mph is about 2400 and this is right under its rated 512lb ft @ 2800 rpms. the higher hp versions of this engine do not make that kind of torque at that low of rpms. Oh btw mine has a edelbrock performer intake with Q-jet carb with manifolds and 2 1/2 flowmaster exhaust. As far as sportiness the truck will outrun a new stock dodge cummins diesel 1 ton. And still wrap the speedo all the way around. It will smoke the 235/85/16 all terrain tires easy.  

The only thing that bothers me about the 502HT is that it isn't fuel-injected.

Going back to the RamJet 502, this is what GMPP says:

With an 11" fuel-injected intake manifold flexing out of the top of a 502" big-inch Rat, the GMPP Ram Jet 502 is just plain cool. Not only attractive, the Ram Jet intake adds a significant amount of function to the big-block with amazing throttle response that you just have to experience to believe. Combining our aluminum-headed 502 with a modern fuel-injected intake results in 502 horsepower and 565 lb. -ft. of neck-snapping torque. With the Ram Jet intake, you also have over 500 lb. -ft. of torque available from 2200 rpm on up.

So I'm thinking that it just has a higher RPM tolerance, but performs equal to the 502HT at lower speeds.  

well if you can afford the HUGE price gap then go for it. Just have that tranny ready for the torture of the 502. OH have you herd about the new f.a.s.t fuel injection that bolts on the carburated intake and is a stand alone unit? I called them and talked about it and it sounds like a exellent efi It is not in my budget yet at $2,200 retail but that is for everything you need. It comes with a generic calibration that will run but it is recommend to have it dyno tuned for best power and performance.