Ace-Garageguy

Guess I could master and cast some. Probably sell 2. Maybe. Never mind.

Hmmmmmmm...not what I immediately thought.

Hey man...there's an awful lot of gearboxes out there, and lotsa different flavors of the Hydramatics. Kinda impossible to remember all of it every time.

No, actually. 1) His build of a Grand Prix requires a Slim Jim RotoHydramatic, not the big Hydramatic. 2) The B&M conversions most typically used the earlier Hydramatic cases with removable side covers, as are in all the kits featuring them. The Super Hydramatic, which would be correct for a Bonneville or Star Chief, has an entirely different case with no removable side cover.

THIS IS THE SUPER HYDRAMATIC FOR A BONNEVILLE OR STAR CHIEF

SLIM JIM PHOTOS: THIS GEARBOX IS CORRECT FOR A '64 GRAND PRIX, VENTURA, or CATALINA...NOT A BONNEVILLE OR STAR CHIEF

The gearbox in the '59 ElCamino is the big Hydramatic. I believe you said you're building a Grand Prix..."By the way, this is for my '64 Pontiac Grand Prix project folks, if that makes any difference." If so, the gearbox you want is the Slim Jim Roto Hydramatic.

The trans photo you asked about is a Slim Jim Roto Hydramatic trans for a '64 short-wheelbase big Pontiac, as I explained above. The Bonneville would use the bigger Super Hydramatic, as I also explained above.

Yeah, the GP supposedly used the "Slim Jim". Neither of those Johan gearboxes are really right, but either would be probably as close as you're going to get. The correct gearbox case bolts together in 3 pieces, like zo. Neither of your doners represent this correctly. So whichever one you think looks best, well, there you go. A somewhat more accurate appearance might be obtainable by mating a manual gearbox bellhousing to whichever one you choose.

Yup, looks kinda like the short-tailshaft version of the Roto box in Tempest . And here's a thread on the big-car Slim Jim...

Not necessarily. The Johan Olds mentioned is supposed to have a "Slim Jim" Roto Hydramatic. I'll need to pull the kit and look, because "supposed to" doesn't always mean "does in fact". The bigger Super Hydramatic (Star Chief and Bonneville) isn't in anything, far as I know...but you could build a passable example by modifying one of the earlier Hydramatics available in parts-packs.

Kinda depends on what you're building. Through '64, the bigger big cars cars (Star Chief & Bonneville) used the older Hydramatic. Shorter wheelbase big cars used the "Slim Jim" Roto Hydramatic.

Ditto.

Pollen's about the worst I've seen it ever this season. It doesn't usually bother me much, but this year it's making me kinda woolly-headed. Guess that's what I get for going outside instead of hiding under the bead with 200 rolls of toilet paper.

Engine looks good, but I believe you'd have a pretty serious short the way the battery is wired.