First time cam install questions

You usually use a solid lifter to check for piston to valve clearance.

For determining push rod length you want to use the hydraulic lifter because you want a push rod length that puts the right preload on your lifter while keeping the rocker adjustment correct. Make sure your head gasket is in place when you measure.

Summit sells a lot of different pushrod length checker tools like this one:

http://www.summitracing.com/parts/TFS-9001/

And run your oil pump with a drill with the valve covers off to make sure the top end is getting oil before you start it up.