1984 firebird 5-speed transmission

I have an 84 Firebird and im putting in a 400 sbc with vortec heads.
It has a 5-speed transmission and the reverse gears don't work, grinds and pops out of gear.
What are my options with this transmission?
Should i install a 700r4
Should i fix the 5-speed
Is there any other transmissions that will fit?
I was planning on drag racing a few times a year maybe.
Any other opinions would be helpful like if i should put in a different rear end etc. Of course low budget side project.
Thank You

Do not go with the 700R4. this is a GM screw up tranny. not very durable . I would remove the 5 speed and get a complete rebuild. most likely a clutch/plate issue or the typical other parts that should be replaced with wear and time. I have a 84 camaro belinetta 82K miles on it. 700R4 305H engine. just this last week I took it out of storage 10 yrs sleeping. drained out all fuel , put new fuel in , and started on the first crank. I have to do a complete inspection and fluid replacing before I use it again. not many of these around our area ..

If the vehicle is in good condition there are people out there that will pay more for it than you think for this vehicle ...perhaps not Maine ,but from other parts of the country.