If you use tapered Timkin bearings and you get a thou of run-out on each side, it'll be good.
Those soft aluminum chucks are good for playing cards shimming training.
4 aw chucks could also be adapted, as well as the griptrue /adjustable series of 3 jaw chucks.
The other option is to make either a ER40 or ER50 collet chuck that can interchange.
I made a couple of ER40 collet adapters,with some acetyl collets as needed,and I am very happy with it.The down side is the ER40 is limited to a max diameter of 30mm.The are an easy collet to make, 8deg per side(from cl axis) for the body and 30deg/side (from cl axis)for the front cone(60 deg from square) with a groove for the nut extraction.
I also put a register pin in the body so all the collets are referenced.
You just get a blank and bore out what is needed, tapered straight, reverse tapered, what ever is needed. Just a few slots with a hacksaw is all that is needed to close them up. On things that fit neatly, you cam use them as distortion collets, where by you just do the nut up tight with the spanner and the collet distorts holding the part.
There is lots of options.
Of course you could just buy the ER40 collets as well which I have also.
I do like the small print of the taig type chucks, just not their repeatability.
I have the Ø39.6*32tpi thread with a Ø40 register for the 1st 2mm from the bearing.This is because there is quite a range in the Taig thread from a nominal size.
The Taig chucks were set up and a register turned into them so they will interchange on the headstock.