Welcome to CHR!

I love those old Chevy C10 trucks. Most everything will bolt up however; your exhaust will require some "creativity" depending on if you go stock or want to use headers. Stock will allow a good muffler man to bend a nice smooth transition and get you by the frame rails with no clearance issues. Headers will, in all likelihood, require a "bit-o-grinding" on the frame or perhaps a dimple in the headers to clear (depending on the make). I have a '71 and put ceramic coated Hookers on it and there was no way I was going to dimple the headers so I took about 1/4" off the passenger side frame to allow clearance to make sure the headers wouldn't rub. Don't move the mounts back or you'll have firewall clearance challenges (hmmm - how do I know this??) and forward will almost certainly give you radiator clearance and drive line length issues (however; if your using other than the stock transmission, you'll need to have a new drive line made) - use the stock location if at all possible.

Good luck with the big block - it will be a beast and your next problem will be keeping the rear tires from spinning! Fun problem to have - we'll look forward to some pictures!

Regards,
Glenn