What do I fix first?

[alextank8]

which one is better and what is the difference?
If you know where i can get one for a much lower price post a link please
Thanks

http://www.cjponyparts.com/tremec-tko-500-10-spline-5-speed-transmission/p/TKO500/

TREMEC TKO 500 26 SPLINE 5-SPEED TRANSMISSION | CJ Pony Parts

TREMEC TKO 600 5-SPEED TRANSMISSION WITH .64 OVERDRIVE | CJ Pony Parts