Newer plastic style master cylinder

At the time I bought mine, Dr. Diff had the best deal on aluminum MC and adaptor. I initially tried an iron truck MC with 1.125" bore. Too much leg effort for my taste and comfort level. Dr. Diff's was 1.03" - a big improvement.

You're not likely to get an aluminum unit going the reman route - they'll be iron. Rebuilders had issues refurbishing the aluminum bores.

Oh, and Andy's adaptor is very nicely made.