Then there is the whole wild world of creative fabrication. But what is and isn't right there depends on what the car is intended to be.
Mustang ll installations not good on thirties cars as all the ugly is out in the open. Ok on fat fender cars. Gary
I'd have to go along with what Ned said above. it has to fit in with the build plan. Personally I'm not a fan of independent front ends under early Fords fenders or no fenders. They may drive good but look terrible. As far as Vega, Unisteer (sp?) or early Mustang that depends on the build . Build plan for my 31 Vic calls for either an F-1 or early F100 box because that is what my build running a flathead needs to look right. I still may run a cross steer as I do have a low mileage Vega box in the shed and that wouldn't be hard to put together but it isn't in the current plan. I've said it before a number of times and several have expounded on the concept that every piece on the build needs to blend in to the build as a viable contributor to the build both in appearance, function and correctness for the build. If the cross steer setup fits in with the rest of the build and functions the way you want it so be it, go for it. If it doesn't look quite right for the total build go with something that does.
Good god none of the above. 36-48 ford for cross steer or One of those converted hudson boxes from @NealinCA for side steer...
It all depends on the style and era you are trying to represent,I have used the Vega,the Mustang and the f-1 box on Deuces ,I have seen the uni-steer used but I don't think I will ever go with it. HRP
Other good options are '55-'59 Chevy/GMC pickup, '60-'66 Ford Econoline van, '64-'69 Dodge A100 van. The Dodge van box is a GM Saginaw box, set up for side steer--I'd almost bet it's the same animal used on the '60s Chevy/GMC vans that were side steer and beam axle, never had a chance to crawl under one of the old Chevy/GMC vans to look at it. These are all good side steer boxes, and you can still find good tight units that don't need rebuilding.