Valve stem seals can cause leakage especially since they are a rubber type of compound and will crack and break loose. Then lotsa smoke. This problem is fairly easy to fix, that is after you lift that 87 pound intake and remove the heads.

The loss of oil pressure - that can get interesting. It might be as easy as replacing the oil pump drive shaft that rounded off - and of course it wallowed out the oil pump and/or distributor. Then it might be a spun rod bearing (probably not a main) - and I have done that on an FE - or even as bad as a cracked main bearing web. I've also done that. Both times, the engine ran just fine, kinda, that is except for some strange deep internal clunking noises.

Whatever - fix it before you drive it again (you really wanted a 390 anyhow)