You can get replacement parts for the early 3 speeds from Anaheim Gear in Anaheim, CA. But as previously mentioned you could probably find another used trans for what the cost of that part is. Your 67 probably has the short tail shaft (overall length of the case is about 17"). The full syncro Saganaw transmissions and the OD units are about 22". They will bolt in but you will need to shorten the driveshaft.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine