Nice wheelset. Although I suspect that the rear OLD on a Downtube is 135. OP should be able to put 2.5 mm spacers on either end -- I'm assuming that the rear triangle is aluminum -- and still have enough of the axle in the dropout.

To the OP ... it really matters who builds your wheelset. 32 spokes is a lot for a well built 20" wheel. The 32 spoke wheels on my Bike Friday are doing great and only had to be trued once as a consequence of an event waaaaaaay outside the norm.