64Avanti

As long as the change doesn't really show, like a transmission wouldn't, I think changing the transmission is fine. I would rather a transmission change than an engine change in an Avanti. I must confess that I did change an engine in a 63 Hawk when I was in school. I still have it but will change it back to a Studebaker engine (modified).

At a given coefficient of friction a larger pad does not change the torque on the disc. A larger pad could have a higher coefficient of friction and in that case the torque on the disc would be higher. A smaller diameter master cylinder or a larger area on the caliper (or total area of the pistons on multi piston calipers) or a different peddle ratio will help when there is no booster. Of course the combination of all of those things has to result in enough fluid displacement to activate the brakes without excessive peddle travel.

Why a stroked engine. If you want to go to 8000 RPM stick with the stock stroke and get some good rods etc.