I've got a '66 Coupe with 289, 3-spd manual transmission. There is an aftermarket power booster and dual bowl master cylinder installed (front disc and rear drum brakes) and, as I was doing a brake line flush today, noticed fluid leakage between the dual bowl connection the lower part of the assembly (It's not an integral, 'cast' iron dual bowl...I've attached a pic with red circle to show where the leak is). I could easily replace the power booster and dual bowl master cylinder completely, but was wondering if it's possible to just remove the two attaching nuts, take the existing (poorly engineered) master cylinder off and replace it with a new, 'cast' dual bowl master cylinder? Appreciate everyone's thoughts/ guidance!

 

You should be able to reuse the power booster and just get a new master cylinder.
Just make sure you get one set up for front disk rear drum.

 

Thanks for that, ElkGrove! Much appreciate you sharing your thoughts (and helping boost my confidence to move that way!)..