John4337 wrote
The end with the tie bar lock has stops, the other base piece didn’t.
Measure the depth of insertion on the other end and match it.
The real test comes when you put the way tubes in. Sink them all the way into the castings, check for square and level (not twisted) and then lock it down. If the locking mechanism isn't smooth you might need to loosen those legs and tweak but I don't expect that will be necessary.
This is the time to be real fussy about about dimensions. Square, plumb, level and tight. It will be easier now because the headstock and carriage are out of the way. It will payoff later when you do the alignments.
Nice work thus far. Don't rush to the end.
BTW - the measurement that you ask about will be very close to 48 3/8" as will be the way tubes.Whatever they are, measure the diagonals for equality.
