I make mine narrow, 28"ish, 2X4X3/8ths thick (thick enough to drill and tap when necessary), i have 6 legs, adjustable 1" allthread, and it sits 14"ish high. I have 3 crossmembers, middle one sideways and sits down about an 1" so it can't interfere with anything sliding on the top.
For whatever frame etc that i am working on on the table i make attachments and tackweld them to the table.
If we were making mutiples of the same frame then we could purpose-build a jig for making that frame, but we aren't and that is why the basic table is as simple and generic as possible then i have the ability to add whatever i need to meet the requirement.
For instance, a Model 'A' frame with a banjo is entirely different than a Model 'A' frame with a 9" rear.
The reason it is narrow is being able to get close to the work piece without banging your legs or leaning out and reaching.
After i position the workpiece onto the table i weld a couple locating tabs that get thru bolted to studs on the table. Then when i take the frame off the table to weld underneath and drop it back on the table it gets relocated by the studs and all is again square and true.
The table is the 'ground height', if you stand on the table you will see your project as completed and when figuring heghts etc you will work with 'real world' numbers and you won't have to remember to add or subtract. You do have to know with certanty the height of your front and rear tires, once you settle on them you can start making the fixtures for the table.