Help understanding what printer I would need

[curious aardvark]

to start with prusa mk3 is a great printer - but not a large build volume. You'd have to split a human head in 2 or 4 pieces.

Ideally you'd want to do a mould in a minimum of 2 pieces.
were I you I'd look at the formbot t-rex 2+
large enough build volume to print a head in one go. Dual independant extruders let you use soluble supports or dual material/colour prints.
https://www.formbot3d.com/formbot-la...ize_p0018.html

Depends on what way round you want to do it. Print the head and make the mould from that. or direct print the moulds themselves by removing the head from a block in cad software to produce the negative mould.

2 ways of doing the heads.
you could get a decent scanner: https://www.scaninabox.com/

https://www.imakr.com/us/936-scan-in...d-scanner.html
scan in a box is probably the cheapest scanner it's worth getting and would do a very nice job
seriously do not bother with anything cheaper or anything that is NOT a structured light scanner.

Guess you'd have to pay people to use their heads - that said it does open up a whole range of options to tie in with porn stars.

The other way is to get a digital artist and have them 'sculpt' virtual heads that can be used to print the 3d models.

But either way a printer that can make a human sized head in one go is essential.

So for a full scan and print setup you're looking at less than $5000.
Or 5 heads.