T56 Trane mods
You could use a QuickTime bellhousing, modified, to connect it to a Slant Six.
As noted above, the T56 is somewhat of a mess when it comes to ratios. For most vehicles, the 6th gear is just too tall. On a Slant Six car....I think it would be unusable.
The best ratios came in the Hellcat Tr6060....the 6th gear is around .77. In that trans, all 6 gears are truly viable gears.
I don't mean to be a dick, but this is one of those questions where if you have to ask....it's probably beyond your budget and capabilities. Couple that with the fact that it's not the best trans and it is a non-starter.
Also, the T56 is gonna be a lot heavier (weight) than you'd need for a Slant Six. Most also don't have a gear type speedo drive so you'd have that to contend with, too.