For a while, I ran an early seventies all synchro three speed with factory floor shifter. Can't remember for sure if it bolted to the original bellhousing but I think it did. It worked well, but I did later run across an early slant six cast iron four speed bellhousing and used it to swap in a four speed with 3.09 low gear. With minor suspension and engine mods, it was one of the most fun driving cars ever.