is the 5 speed in the v8 the same as the v6

Most likely yes.

1984 was the first year for the use of the Borg Warner (now Tremec) T-5, five speed, overdrive manual transmission. Outer dimensions are very similar on the two transmissions, but they differ in a few key respects. First they have difference input shafts. The v8 tranny uses 27 splines, the v6 14. This can be overcome by using the correct clutch kit for the trans, regardless of engine. More importantly, all of these boxes were notoriously weak and the v6 versions even more so. I cannot recommend putting any t5 behind even a mild 350, yet alone a v6 version.

no spline shaft was larger on V 8