Small block distributors with adj mechanical advance

Just wondering what options are out there for small block distributors that have easily accessible adjustable mechanical advance, both different spring rates and total mechanical advance.

I have an MSD distributor in my Barracuda but the 66 Valiant I am putting this into needs only about 10-12 degrees mechanical advance in the distributor (running on propane and want to run 16-18 degrees initial) and the MSD doesn't have a stopper that will get down to that little advance which is annoying.

Any advice appreciated.