273 to slant 6 conversion

Yes, I know I am asking the opposite of the normal question. I have a very nice california 1965 barracuda that I will be keeping for a long time. It has a 273 upgraded to commando specs, a stock 904 floor shift, PS, and a horrible aftermarket power brake kit (but still 4 drums).
I am removing the power brake kit and the more I work on this car the more I think about simplifying it. Go back to manual steering, manual brakes........and create a bunch of room in the engine compartment by installing a good running slant six. Crazy, I know.

Will a slant six bolt up to the trans in this 273 car? What converter and trans changes are required?

Thanks.