Mark,
I did verify the A-Sweep board in the MOD 703K matches the part number of the board used in the 453A-5, part no 670-0417-06. It looks like the main change may be the calibrator, so hopefully the parts you recommend looking at align with the other revs. The change doc indicates changes for serial numbers > B02100 and the ones I have are B021516 and B021836
In comparison, the MOD 703H has a 670-0417-02 board. The change doc states it should have the same board as above, for serial number >60770 and this one is 60794.
I have an original manual coming so hopefully the board layout photos will be easier to decipher.
