[markeb01]

I’m not sure I understand what crossmember he is talking about. If he means the front suspension crossmember, it certainly is strong enough because with side engine mounts the engine IS being supported in the center of its mass right over the crossmember. In the original 1960-62 configuration, the engine was supported by the bellhousing crossmember and a front mount. Once side mounts were introduced with a small crossmember under the transmission, the bellhousing mount design became obsolete.

Unless you want to swap in a manual 3 or 4 speed using the original bellhousing, any modern transmission will require a new crossmember under the transmission tail housing. The original bellhousing crossmember needs to be removed for clearance. The side mount/tail housing arrangement has been in service for decades as standard equipment so it’s certainly a proven design.

I’m not a fan of Powerglide transmissions. My 67 Chevelle originally came with a “Slip-o-glide”. Low gear always ran out too soon, and high gear was too high, so when the engine bogged on a hill all you could do was slow down enough to go back into low gear. Climbing any steep hill or driving with a full capacity load became very annoying.