Im in the process of putting my tpi injection out of my 86 Z with a cracked block on an 84 305 HO longblock. Are there any differances in compression or anything i need to worry about? Im also putting a new cam in it so should i set the timing at 0 or should i advance it and if so, how much should i advance it? Would i notice any performance gain? I run 93 octane or at the least 92 octane if i cant get 93 all the time.

Basically the same engine with different induction. Both had 9.5:1 compression. The '86 will have a one-piece rear main seal, the '84 a two-piece, so the flex plates will be different.

It depends upon exactly what cam you've got, and the recommendations from the manufacturer, but the typical practice is to install it straight up.

The high octane is probably a waste of money. If it doesn't ping on the lower stuff, putting higher octane in won't help performance (can actually lower it).