pushrod length/measuring question

Yes - that's basically it. TDC on compression stroke. It depends...lol. When I measure and call Smith Bors. I measure overall length and tell them what radius the ball and cup need to have. They take the info and account for it.
If you are using Comp's ball method then you will need to subtract the diameter of the ball from your figure. So fit the adjustable pushrod in place and snug the pushrod's lock nut. Then remove the adujustable pushrod from the engine by backing off the rocker shaft. Then drop the ball in the cup and measure. Then subtract the ball diameter from the overall length.