Your best bet for a mechanical 4x5 head is a Chromega. I just overhauled one. They are built very well and in the USA they are very plentiful.
You can get a chassis to put it on for free if you look enough.
I'm going to end up having to wait.
1. don't have the space to store an enlarger right now, can't even think of using one at home right now ;(
2. I'll consider that. I have some saved searches on the bay for devere and durst 4x5 enlargers. So one day the right one might come about. I'll use it for b/w only though.