I would hazard a guess that you may in fact have to lengthen a TA22 drive shaft if you are fitting a 1G to a RA23. I also reckon that the splines on a '22 driveshaft are different to that from a '23 two piece unit.
And yes, why would you bother when a '23 unit is a direct fit?
It is for my RA23 with 1G-GZE.
Cheers,
Mitch.