I’ll answer the questions but suggest this is the wrong way to go about doing things because of other issues, real and possible that can/will/might show up.
This Maneuver is basically bass akwards.
1: New pushrods should be purchased on most every build with a new cam unless all things remain the same from the original configuration.
2: The question of compression and pump gas is mostly a loaded question. Generally speaking, without knowing the rest of the engine combo, a general hot rod build up and 9.8-1 is probably (and I grit my teeth when I say this and winch my head away) OK with 93 octane. (And again I grit my teeth, cringe my eyes closed and turn my head with possible regret on saying that because of the wide range of possible combination screw ups that loom.)
You wanna run ANY grade octane?
Then the ratio your looking at is 7.5-1.
3: Cam clearance will milled heads and a milled block? This answer is again a semi loaded question but I’d say it would be OK. HOWEVER! You need to check with some clay on the piston top, pump up the engine oil pressure, rotate the engine around a few times and then check clearances.
IMO, this is a bad path. I understand money is an issue but going this route could end up badly. If you do this, check everything on every step of the way or you could just be throwing money into the garbage can.
