TH400 trans vacuum modulators

[Robert1970C20rstbukt]

A couple weeks ago I replaced the old, huge vacuum modulator on the TH400 in my truck and now it shifts really fast, I'm talking 1st to 2nd at like right below 10MPH. The old style ones have been discontinued and the replacements are friggin small, like 1/3 the size of the old ones. The bad thing is the shift points on these aren't adjustable, they don't have the screw sticking out of the end. Can the old style ones still be bought somewhere even though they're discontinued? Every dam* place I checked at only has the stupid small ones. The tranny is a '67 out of a Chevy Caprice if that matters.