Those running Trickflow 190s with a hyd roller

Yes, you will have to open up the pushrod tunnels.

The only correct way to measure pushrod length is just that, measure it. You need an adjustable pushrod. You can make one real easy or buy one.

Set the adjuster at 9/32 inch protrusion from the bottom of the rocker. That should be no more than 1 thread showing. Adjust the adjustable pushrod so there is zero lash. Measure it for over all length and add .050-.100 for lifter preload.