You could get the Haynes manual 69-84 Chevelle book, It is quite detailed and covers all parts of the car, lots of good pictures and factory drawings. The heater core swap is not too hard, did one in my 77 Monte with no instructions, but they would help esp if the car is nice and you don't want to break something beacuse you don't know how to dissassemble it. Also the original dealer shop manuals and factory assembly manuals are available from the resto companies for your car, they are more costly than the Haynes manual which I got for $15?? at autozone.
I just did the heater core on my 71 and it really wasn't that bad a project, but my entire dash was out and I can imagine it would be a great deal more difficult with it in. The Hayens manual is better than the Chiltons but it doesn't really give that many pictures. Definitely get something before you attempt this, and be carefull because you don't want coolant on your interior.
It is usually a major pain in the gluteus maximus to change a heater core. This said, do the job properly when you take out the core. Replace the gaskets, fix any rust, repaint it etc. while you have the thing apart. The parts aren't expensive - it's just the work involved. Best bet is to pick up the service manual (as has already been suggested), and go to it. Good luck.
One thing I would suggest in addition to the instructions in the service manual. Go ahead and take out all or most of the bolts for the inner fender liner rather than prop it open with a 2X4. It takes less overall time and makes access easier and cuts down on the skinned knuckles. Steve
A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!