1967 was a transition year. 6 cyl trucks had the short tail housing Muncie with the non syncro first gear. If you have this transmission the driveshaft will need to be modified to accept the longer Saganaw transmission. It may also require a fine spline front yoke. Some of the later units had a larger front bearing retainer so it may be too large for the hole in the bellhousing. The side cover is different as you indicated and will require some modification to the shift rods & arms. Otherwise it will "bolt right in".
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