Hi Chris,
On my 352 gearbox the bolt you're on about is a metric one, M6x1.0. (10mm spanner) It's about 30mm long, just over an inch although it's not threaded all the way so I guess a 25mm one would do fine.
Oil filters I can't help you with because I guess any part numbers I have will be completely different over this side of the pond. The one in the spares cupboard is a Fram filter, FB2099 and they were fitted to lot's of 60s & 70s Fords, Rover, Opel and Vauxhall cars. Nothing special, very common over here even now.
Brian