Thanks. Yup, a Ford 2-wire IAC. Takes filtered air and sticks it right into the intake. Doesn't seem to work as well as the 4-wire IAC on my Skylark, it only seems to have 50% of the range it should have. I think I may have some setting goofed but haven't figured out what yet. It works good enough to get high idle when cold and does minimal work when the MegaSquirt is modifing ignition timing to target idle rpm.

That fuel pressure regulator is the external oil pressure regular to the lash adjuster galley. The hose going to the oil fill tube is the by pass line. While testing I reduced the feed line to 1/8" while maintaining a 3/8" drain to let it keep better pressure control and minimize oil bleed off the pump.

Not sure what there will be to adjust with the tune based on crankcase pressure.

I didn't measure the piston wall clearance.

I just finished lengthening the wiring harness so that is ready to go.
Rebuilding an OHC Pontiac 250 with EFI and a Turbo