I would certainly give Fox a call on the gaskets...and they'll probably come with screws. You can hopefully get socket heads to use instead. If it comes right down to it, you can make a backplate gasket very easily. Some use postcards, 3x5 file cards, or playing cards. For the head gasket, I would guess that any .15 sized head gasket will function fine. Most .15's are really metric bore and stroke.
The glowplugs you want are SHORT reach. I would definitely NOT use Fox glowplugs. Thunderbolts, K&B's, Zinger, Merlin (from Brodak), etc., should work much better. Hot glowplugs are good, and 10% nitro with mostly castor oil will work well.
Steve