Sanden A/C Compressor to fit a 273

If you have U pull junk yards you could look for n 80's 5th Ave.

That will have a sanden bracket for a 318, which will work.

A small block truck is a possible option, too.
Up until 91 I think.
that's a possibility, and yeah the bracket set up from late 70's thru 91ish would work with a little futzing about.

the support struts attach to the intake manifold, so you'd need an aftermarket or a stock 318/360 from that time. the alt mount is different and frequently takes a different style (GM) alternator, that's 50/50 there.

then there's the timing cover/waterpump/pulley/radiator considerations. i *think* it might work with a stock cover and pump, without the timing mark being too obscured. but unless you want to run that whole set up wholesale, you'll definitely run into some compatibility issues.