What boost are you building for? Unless you are going over 12-14psi, the Starion oem or felpro 88-89 SQ are fine, and have more research on sealing than any metal gaskets except annealed copper with orings and water sealants.

I like your head type choice, but are you sure of the no jv's? my 85 truck hydraulic head had jv's. I think you can get Clearwater to deliver a no-jv head with hydraulic valves and rockers, if you just ask. That is my head of choice, with just a little clean up in the valve bowls, leaving the already to tight short radius strickly alone. Much more benefit from smoothing the outside of the air path curve, the top of the valve pocket. Just clean up core lines and casting trash. A high polish is actually not as good as a matte surface for air flow.

Freeze plugs are easy if you can get access. If you are paranoid, take this step first. drill a hole in the middle of the freeze plug and screw in a sheetmetal screw, then remove the s/m screw and screw in an eye'ed screw thing and tie on a piece of wire in case you drop the plug inside when you drive it. Now, drive the plug into the block, AND try to pin it against the inner block core. Easier than it sounds. Skwiggle it sideways a tad and get a good grip on a freeze plug edge with a pair of vicegrips cranked TIGHT. Then turn the plug sideways and pull it as far out the hole sideways as you can. Then use a prybar and maybe a wood block fulcrum and pry the plug out. Comes pretty easy, with the right wrist snap on the pry bar. Stick it in your eye on the way out to remind you to wear safety specs. BTW, I never drill the hole and tie it up. Can't fall far, and not much of a prob unless it's brass...