pushrods

Would be easier with intake removed. If the lifters are used and full of oil this could be a PITA

But you can get a fairly workable idea by checking "the 4 corners" of the engine. As if you are setting solid lifters, use the "EIOC" method, that is

Bump the engine until the EXHAUST just starts to OPEN and check the intake on that cylinder

Then bump the engine until the INTAKE has opened and is nearly CLOSED and set the exhaust for that cylinder

Measure the height of the valve retainer with a dial caliper, etc so you know what it is "closed."

Then stack feeler gauges under the rocker until you have the lifter bottomed but the valve is still closed. The stack of feelers will give you the depth at the valve IE 1.5 X the lifter movement

The trick with the intake on and with used, oil filled lifters, is to get them to bleed down and make sure they are bottomed, and to "not" open the valve.

Unless you've had the deck / heads milled, that is, if you are using "a standard" combination, you 'should' be OK