Late 140/164 bosses are the same as 240 bosses (spline count, etc). Speaking of others -
1800s are different from late 140/240.
740/780/940 are the same as each other.
760/960 with adjustable columns and the wrong-wheel-drive stuff are different to 740/780/940.
Go with whatever works for you - you are the who will be driving it and looking at it.
By 'genuine Volvo boss' - do you mean an OE boss for fitting an accessory wheel?