it the engine is stock and the valvecovers are the center bolt type
it's a 1 piece rear seal..
depending who you talk to, they changed in 86-87
in a light car, with traction issues
a 10.5" will be fine, if you do clutch dumps, I'd get a scatter sheild over a bellhousing..
under the car with the inspection cover off the trans(if it's even there) you'll be able to see if the engine is 1 piece rear main seal.. with a flashlight.. you see alum bewteen flexplate and engine it's 1 piece