Need 1998 AX4N

[1998 SHO]

Looking for a AX4N to rebuild or already rebuilt. I want to replace org with updated parts before I pull the org. Does anyone have one on for sale or does anyone have a upgraded kit# that you could recommend for a performance upgraded. I plan on a brazed TQ, Shift Kit, better clutches etc. There are many kits to choose from and I can not choose a kit that i am happy with. Would like to do this myself with a mech that has the tools. Car and trans has 67,000 org miles. I'm having that nuetral condition after a stop. I have a lot of work into car and it is very very good condition, 1 or 2 scratches and one small dent, org tires. I'm the 2nd owner after 54,00 miles. I have cams welded. Also, would a AX4N form from same year work (I know SHO uses different TQ, more clutches etc) for the rebuild if SHO parts are installed. Has of now the only forward gear I have is 2nd but once speed is up to 10mph I can shift to drive and car pulls hard with no slipping thur all gears, but drops to nuetral once I come to stop, also there is no reverse at any time. I'v read that there is a TBS about a Forward Clutch Piston leaking. Any help with rebuild, What condition is trans in.