BL engine and box swap - possible BK to BL driveshaft assembly variation.

Recently had a low K BL engine and box installed in my BK. Engine is running well. BK engine was shagged at approx 255000K.

Discovered what seems to be a intermediate driveshaft assembly variation between BK and BL that introduced some minor issues and thought I should post for feedback and possibly assist others.

In short, I got a failed gearbox seal and gearbox oil leak as a result of lateral (not radial) intermediate shaft play. On investigation the excess shaft play is reported to be due to a variation between the Bk and BL carrier housing - other end of the intermediate shaft to the gearbox.

It is my understanding that I have a BL engine, BL box and BK carrier housing. After reviewing assembly diagrams and consulting with mazda my agent concluded the resulting fix was to install a 3.5 to 3.8mm shim in the carrier housing to restrict the lateral play.

Not being a hands-on mechnical expert myself I'd welcome feedback from those familiar with the assembly of each model.

Apart from this hiccup the swap has been fairly trouble free.