I expect all the long studs for the TF270 heads to be the same length.
These are my quick measurements of one head. The head thickness at each bolt hole.

And if you want to estimate the amout of exposed threads above the nuts, I use:
(0.430 Nut height, 0.120 Washer thickness, 0.040 Gasket) and whatever the coarse thread length is on the studs into the block.