building a gen V 454 motor has been balanced and bored .030 forged speed-pro dome pistons running a crane valve-train and the 420 cam heads a 117cc oval ports with 2.19/1.88 valves since I have switched to a mark IV style valvetrain I am using Mark IV push-rods(lenght is a little longer then the Mark V) comp ratio 8.79-1. I haven't started the motor but if i make the valves to tight will they hit the pistons and lock the motor?

The length of the push rod shouldn't matter with your lift. Your still adjusting the rocker arms on the mark IV set-up, were the length becomes a concern is how the rocker arm runs on the valve stem. If your running the stock style stamped steel rockers I wouldn't worry about it, if your running roller rockers you need to pay closer attention to how the rollor tip rides on the valve and get the correct valve geometery.

I would have checked the piston to valve clearance when I assembled the engine.

Cam timing has a distinct effect on valve to piston clearance. it should be checked when the cam timing is set and a weak checking spring can be used on the valves.

Today I pumped it up to full oil psi and adjusted the valves nothing hit installed the plugs everything seems to be ok now just have to wait for some shine and I will put it in

i wouldn't put an engine together without checking piston to valve clearance!!!!!