Chassis crossmember

Written In the chassis assembly instructions it states the mid crossmember is not symmetrical and to look at drawing IOS 01 c for the  correct way round to fit it.
The problem I may or may not have is my 4 large countersunk holes are symmetrical and don't match the measurements on the drawing  at all !
My innermost holes are at approximately 135mm centres from the end of the crossmember as opposed to the quoted 116.50 n/s and 156.50o/s.  
Has anybody else Come accross this discrepancy, or is it just a modification ?
GARY

There was a mod at some point, I know I had to drill an extra hole or two in the middle crossmember. I think it was for the tanks