Thank you for this brilliant idea!!!
I could not find any "thick" glass around here but bought some 3/32 11x14 glass from Home Depot for $3.50 and added a 16x16 porcelain ceramic floor tile for $3.45. I epoxied the glass to the ceramic tile and got a nice solid flat surface for the head surfacing.
Warning for those going to Home Depot, the Red 3M sandpaper that they stock has a plastic backing that MELTS when you put the contact cement on it! They do not carry any of the old Wet and Dry paper anymore I had to find an actual hardware store to get it at $2.00 per sheet. The good news is starting with 150 then 220, then 320 it only took three sheet changes total. I did both heads on each paper, cleaning and alternating heads every minute or so to keep things even. The results were excellent!!! Nice flat, clean, and smooth finish. The weight of the heads does the work keeping things flat and even. Very impressive results.
I used a sanding block and the Red 3M paper to block sand the surface of the cylinder block, exhaust and intake ports. Same sequence 150-220-320. Results look good.
Thank you again for sharing this setup and method. This is the biggest DIY job I have done in quite a while and getting the heads right is a big part of making it work.
Terry
Here are some photos: