Spend the least amount to keep it running strong and reliable. I've seen the Victor Reinz gaskets used for Cummins rebuilds. I would see what the modified-stock truck pulling guys are using for gaskets, wastegates, trans stuff, etc.. just for curiosity.

Keep the tow rig strong and reliable so you can be sure to get your awesome Belvidere to the races. Spend any saved cash on racing!
Mitch