Your old toyo gearbox utilises a simple strainer - its not a filter by any sense. You can reuse it as long as its not torn. Clean it out with something and reverse flush it to dislodge any debris in it.
for the gasket, buy a new one or make one with good gasket paper. I have used threebond 1207B (toyo FIPG) on this area and it set up extremely well, if your transmission sump has the original rubber/metal gasket on it and its not damaged you can use it as long as your sump is perfectly straight (check it on a piece of finished marble) - for RTV sealing the gasket return this and buy some permatex ultra black if you can. Please read the package carefully - there are two types of products, one gives a total time 8 minutes, one gives a time of 2 hours, Time your work and refill accordingly, meaning if you use the 2 hour one do not refill atf until 3 hours have passed. You will also need some acetone to clean the sealing surfaces. I always used two guide bolts to align the sump so it can go in perfectly straight and it does not move around while trying to thread the bolts.
The guide bolts are pretty simple, get two longer bolts with similar threads and cut off the heads, screw the shaft into two holes and leave them there, install sump bolts and remove these two, then install the original bolts back and torque everything down.
If the gasket is not good, then get a new one - it holds no pressure - it just prevents leaks around the sump, please tighten the bolts with a "10 ka screwdriver" only the bolts are only gently tightened in a cross fashion.
