It's easiest if you stick to the same manufacturer - but not always necessary. It's also best if it's the same size machine so you don't have to alter the size of the hole - but again not necessary.
Also if fitting a head to a different cabinet you'll need to make sure that the wheel of the treadle and the wheel of the head line up plumb so the belt can travel in a straight line. This may require some alteration of the cabinet.
Another option is to get a set of treadle legs, build your own top with a hole cut to fit your machine lined up with your treadle legs, then pop a coffin top over it as a dust cover (instead of building the top with a drop mechanism).
I've got a few treadle bases that the tops were either too far gone to restore, or no tops at all. For one we purchased a butcher block top ... well just because we thought it would look nice ... we still need to cut the hole and set it to the irons. I first need to decide which machine I'm going to put in it though .... that would help!!
I have a set of Wilcox & Gibb's irons that are gorgeous and we're waiting to find the right top and machine to pair it up. Sometimes good deals like those W&G irons come along and you can't pass it up and yes I'll probably pay more than I would have otherwise for the head and top but will make out in the long run as the irons were only $2.00.