Was doing some research on transmission conversions on 90's vehicles. Wondering if anyone has any recommendations on brands for a new transmission and parts. Since I would have to take the exhaust off to fit the new tranny I could use some recommendations for aftermarket exhausts for a 98' XJ8.

 

it's a bit specialist - I've not seen a forum member carry out a conversion on these cars, and considering the transmission issues with the ZF fitted, that can only mean it's very difficult.
Reason - the car's electrical system, it has something like 13 modules linked, take one away the car is a brick.
There are black boxes out there that can trick the system, but these are costly and I know next to nothing about them.
Manual transmissions, the Getrag fitted to some M cars, and a pedal box assembly from a manual X300 or XJS might aid the mechanics - but an adaptor plate will need to be made.
There is a manual + LS converted car on youtube that mentions the hardware in some detail, I suggest you watch that, and digest the sums mentioned on the conversion.

Good luck and let us know how you get on.

 

Also this Franken-Jag