The front driveshaft will be the issue ,the 65 K20 front driveshaft hooks up on the passenger side the later TC is on the driver side.You could possibly buy an adapter to install a NP205 to the allison or the ZF.Try
www.advanced adapters.com that's where I purchased mine to adapt a 4L80E to the NP205.I also used 73-87 front and rear differentials to gain the turning radius and durability.She's not all done but making progress.
