I swapped rear ends on my 78 camaro. went from 2.73 to 3.42. since then I am running down the highway at 65 mph @ 2800 rpm's, and the engine starts to get hot, will the 2500 stall converter help this? I'm on a limited budget I have heard there are modifications you have to do to put a 700r4 in, or is there another tranny I can find to bolt up and go? maybe I need a bigger core radiator also, and what size fuel pump should I be using? any ideas on what vehicle carries a bigger core radiator that will bolt in to the camaro?

Tranny is a TH350, engine is a 400sbc, torker intake, holley 600, summit cam and lifter set- specs:

Brand: Summit
Product Line: Summit Cam and Lifter Kits
Part Type: Camshaft and Lifter Kits
Part Number: SUM-K1106
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 3,000-6,200
Intake Duration at 050 inch Lift: 234
Exhaust Duration at 050 inch Lift: 234
Duration at 050 inch Lift: 234 int./234 exh.
Advertised Intake Duration: 292
Advertised Exhaust Duration: 292
Advertised Duration: 292 int./292 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.488 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.488 in.
Valve Lift with Factory Rocker Arm Ratio: 0.488 int./0.488 exh. lift
Lobe Separation (degrees): 114
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: No
Lifters Included: Yes
Lifter Style: Hydraulic flat tappet

and 275/60R15 firestone firehawk indy 500 tires on the rear. help please!  
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Sounds to me liek your cooling system can't handle the motor now. How big is the radiator you're running? What kind of water pump? What coolant mixture are you using? What temp thermostat?  

stock water pump, stock fuel pump, stock radiator, 70/30 coolant mixture, and a 160 degree thermostat.  

Are you saying that your Camaro didn't overheat until you changed rearends? That is strange. Did you do anything else to the car at all before, during, or right after the rearend change?