my 283 is running hot

[76 k10]

i just put in a rebuilt 283 in my truck that i built about 2 years back but i droped it in my truck and i put a pretty good size cam. but my prob is it think its geting real hot cuz ill start it up and it will be as choppy as a full on dragster then once it worms up it gets alot more thumpy and then ill got for a drive and then the loppe gos away could it jusat be that its a new motor? i no everything is fine with the insides

[VileZambonie]

Check your ignition system thoroughly and set your timing. Make sure it isn't running too lean. Check your thermostat.