Well for me its raised cam 60MM cam. Lifter bores can be stock but the pushrod is not the straightest and clearance for a proper sized pushrod for something like you would build is tight. Also tie bar lifters make getting a bigger pushrod very tough. But it can be and has been done. Ideally you woudl want to spread the lifters out to straighten the pushrod and do with a keyway style lifter. While you are there you can move the lifter diameter to .937" or 1.062", which also gains a larger diameter roller wheel. You can do 655" with a 5" crank or another option is a 645" which is a smaller bore of only 4.530" which will leave some room for later. FWIW my current build is a 596" for brackets.