I'm pretty sure it will fit.
I never really understood all the designations in the 45MX line, but from what I've seen the chassis are all the same.

I too prefer the condensor head for B&W, except for very contrasty negs or grainy negs where I wanted to subdue the grain somewhat.
But for proofing or non-critical B&W work, I always stuck with VC paper and dial-in contrast of the 45S. Easy peasy.

To switch over from one to the other is a snap. Well, 2 snaps and a plug exchange.

Notes on the 45S Dichro head:
I had a lot of light spill from the bottom and back of the 45S head, and masked those areas off with (black) Ilford bags. The "white light lever" seal is not very light tight, and neither is the fan. Also the filter dials in the front are way too bright, just put a (black matboard) flap over it.

Also I replaced the standard EVW bulb (250 Watt) with an ESJ (85 Watt) to reduce light output for making smaller prints with reasonable apertures and times. When needed, I would switch back to the EVW.

https://www.interlight.biz/light-bulb/ESJ
https://www.interlight.biz/light-bulb/Evw

Since all those heads are very heavy you'll spend a considerable amount of time to align the whole thing square. There is quite a bit of sag, because of all the weight, and that needs to be compensated.