I suspect you might discover the bolt pattern on the rear of the block will match that of later model Chrysler OD transmissions. Considering the cost of any transmission conversion (rebuilt trans, driveshaft work, labor, misc. parts), you'd have to drive much more than a few times cross country to even get close to recouping your investment in making the trans swap.
The OTHER thing to consider is what you're cruise rpm will be in OD. It is entirely possible to have that rpm be too low when running at 55mph in OD for efficient engine operation with that load. Even a 3.54 ratio with a carburetor would be marginal, probably so much so that it'd be going in and out of OD in some situations--which is not good for economy or the trans. Considering how the early TorqueFlites would not downshift from high gear until low speeds resulted in a regular 3-2 downshift (not a WOT kickdown downshift), you might get up to about 30mph and then suddenly kick the throttle to about 2/3 throttle (or just to the edge of forced kickdown) and see how it handles that situation, except consider that what'll really happen will be a little slower as it will start from a higher road speed and higher wind resistance. Remember, too, that just because you drop the rpm with relation to road speed might not result in a really significant drop in fuel
consumption, especially if the engine is lugging and going into the carb's power mixture to just moderately accelerate up to speed when in OD.
Of course, the GM trans will use vacuum for part throttle kickdown modulation and there is also a kickdown cable on the Turbo700. There are also a couple of vacuum switches to lock and unlock the torque converter too.
I know, many people love that GM Turbo700 for its deep low gear, but that deep low gear also makes for one huge chasm of a gear spread between 1st and 2nd, in my orientation. If any sort of smoothness is retained, it'll most probably be due to clutch slippage during that gear change and not specifically from slippage in the torque converter (as some have mentioned elsewhere).
Considering, if I've been led down the correct path, that the early Hemi bolt pattern is the same as the later A-block bolt pattern, something on the order of a 1980 or so TorqueFlite has the most clutch plates and such of any of the similar A-904 family of transmissions. A few years later, the OD versions came online. I suspect it might be earlier to interface a beefed up Chrysler transmission with your vehicle than a GM transmission with lots of extra hookup items. All it takes to work the OD on the Chrysler trans is a little electricity. The torque converter lockup function is purely spring vs. fluid pressure, if you decide to get one built with the lockup converter. Typically, the HD vehicle applications were not lockup transmissions, which has some plusses also, from my own experiences.
There is a 2.74 low gear set that a trusted transmission builder has told me is as strong as the regular 2.45 low gear gear set. Still, though, the key item with any OD application is the existing rear axle gear ratio. Remember, too, that OD applications for vehicles when your car was built used something on the order of a 3.73 or 3.91 or 4.10 rear axle ratio so the cruise rpm in OD would not be so low as to be out of the torque band of the engine.
As for the parking brake situations, it might be that backing plates from a '65 or '66 Chrysler 8 3/4" rear axle might work on the earlier rear axle flange. There might be some information on this on the "Forward Look" website (the Chrysler website and not the "other" website that is ".com"). I know there is some disc brake conversion information in there so there might be something about the parking brake issues too.
Just be forewarned that having an OD trans is not always a big money saver on fuel, especially when savings are positioned against what that whole deal might cost in the first place. Not to mention the possible decrease in value of an "altered vehicle".
Just some thoughts on the reality of that whole situation,
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