I have a 1991 "mexican" block 5.0 running engine.
I want to put aluminum heads and a bigger cam in it.
How Big can I go without hitting the pistons?
X cam?
 

I will order springs with the cam kit.
I will measure pushrod length when I install the new heads.
Don't need vacuum for anything.
I wanted to know how much lift I can use with the stock stroke and pistons.

Installing the cam advanced,straight up, or retarded will
also change P to V clearances.

Intake valve diameter is also part of the equasion.

1.94 will clear where a 2.02,2.05,2.08 wont.

We have used .530 lift with stock diameter intakes
but it wouldnt clear with a 2.02 unless we advanced the cam
to get the int valve to chase the piston down the bore.

I would use .500-.510 for a standard but thats depends how much clearance
you feel safe with.