Stan from VA farmall 230 engine??

You can shave some off the head, if it hasn't been planed too much previously. I would get the valves gone over to be sure they seal, maybe have the head machined just until it's flat, then re-assemble it and check compression again.

100 psi isn't real high, but it is enough for the engine to run just fine, and depending on what you want to do with the tractor that may suit your needs.

I put two pictures in Parts & Pieces (Farmall Pistons Side/Top views) comparing 3 pistons: a x30 series firecrater; a 3-1/8" tisco overbore replacement (advertised for the Farmall C with the C-113 engine); a x40 series firecrater. The x40 series firecraters (on the right in the pictures) or the tisco replacements would obviously give you the best compression, the layout of the domes are very similar with the tisco just being squared off where the firecrater is more rounded. The last several 30/40 series motors I've put together were with the 3-1/4 tisco's which have a solid single level raised step rather than the firecrater looking dome, and a shorter compression height (about .100), so they don't have any clearance issues. I don't think these would either since they are so close to the 40 series firecraters, but worse case would require a little rounding with a dremel tool on the domes.

On the head, if you have the factory 30/40 series head, you already have the shallow combustion chamber version. IMHO If you want your tractor to last another lifetime or two (vs 1 pulling season) forget milling the head and just have them take off the minimum necessary to resurface it.

Hope it helps,
Stan(VA).

The Tisco in the pictures (actually all 3 pistons) are 3-1/8" not 3-1/4". The Tisco is the one you get if you order for a Farmall C with the C-113 engine (3-5/16" lower sleeve OD).

The 3-1/4" Tiscos I referenced in my earlier post look totally different. Again, they are ~1/10" shorter on compression height and have a single level, rectangular shaped, raised step on the head that sticks up maybe 1/4". They are the ones you get when you order a kit for the Super C with the C-123 engine (3-7/16" lower sleeve OD). If you have the original block in your 230 (see part numbers in the earlier thread) these won't fit without custom machining and custom O-rings.

In the earlier thread you asked about the C-135 sleeves since that motor also has 3-1/4" pistons. I was in a hurry when I posted, but they won't interchange with the C-123(Super C block) because the lower sleeve OD is slightly larger than the 3-7/16", maybe another 1/64" (didn't memorize that one). Don't recall about the pin diameters, seemed like some of the later motors went to a smaller pin but I don't have my books in front of me. I have a spare set of C-135 std altitude firecraters at home and could check but that's a whole 'nuther animal.

For the best compression, lowest cost, and easiest overhaul on that block I would recommend the tisco 3-1/8" piston set (just make sure you clean the casting flash/ridges off the top of their pistons to avoid hot spots and detonation). Or if money is no object ;) find a set of 140/240 firecraters.
Stan(VA).