Transmission help...

Hey guys, I have a few questions. I am in the beginning stages of restoring my car and I have come to a crossroad. I am not restoring the car to original specs and I had the original engine torn down, 2 cylinders trashed so there goes that block. I don’t want to sleeve the block since it wouldn’t be worth it. Now since the engine wont be original and the car wont be stock spec I am considering selling the transmission. It is a 1966 18spline 4-speed with Lakewood bell housing. The question is, is before I decide to sell it how much can a 23 spline 4-speed handle? I don’t plan to sale the car and the purpose of this car will be cruise ins and the occasional burn out, I DO NOT intend on racing it at all but I don’t want to hit it and have the tranny explode on me. The engine I want to build will be a warm 440 hopefully shooting around 425hp. Let me know what you think.

The '64 Max Wedge cars and the '64-'65 Race Hemi cars used 23-spline 833's and they held up just fine.

The 23 spline will take it, but are you really going to make that much money by selling the trans you already have and buying a different one? If the one you have now shifts fine I would just keep it.

I'm not one one for making cars all original either, but I certainly wouldn't ever sell a numbers matching drivetrain to a car like that.
I'd keep that block, no matter how bad it is and transmission with the car.
After all it's either a 440 4-speed or 426 HEMI 4-speed to have that transmission, right?