Heater recommentadtion

[J.D]

I want to transplant the heater from something relatively modern into a custom dash.
It needs to be as small as possible, be easy to plumb in (fabricating air ducting is not something that scares me particularly but I'd rather steer clear of too much water plumbing) and have the facility to vary fan speed, temperature and where the air goes, all controlled by decent looking knobs.

Any recommendations?