I've certianly never done it, just some random thoughts off the top of my head that may of may not be useful.

- A late model B20 will have 8 flywheel bolts, and match the crank end on the OHC motors. Thus theoretically allowing you to put a newer flex plate onto the B20. I have a late model B230 flywheel sitting around in my garage (due to go into the 245 in place of the AW71 this weekend*) - I could try setting it on my B20 crank that also hangs around (had a spun rod bearing, I rebuilt the PV's bottom end using another crank). I'd assume they fit, but Volvo has a way of sometimes using compatible parts for decades, and other times making almost imperceptible changes.

- The AW71 bellhousing will (agan , AFAIK) bolt up to the B20, the bellhousing pattern didn't change. However, you will have a pattern as it is designed to set the engine at the OHC angle, not upright in OHV style. And I don't think an AW71 will bolt to a BW35 bellhousing. You might need to have the bellhousing cur and rotated? Or possibly redrill the back end of the bellhousing?

* - I hadn't really thought that far ahead, but I will have an extra AW71 hanging around the joint after I pluck it out of my '93 245 this weekend. I'm putting in a 5 speed (M47) trans. I still have the excellent wooden shipping crate someone built for my M47. Shipping would be spendy, however, I spent $160 getting the M47 (and flywheel/driveshaft/pedal box/etc small parts) from the west coast to here. I wouldn't want much over shipping for it (just a way to get it out from under foot!). Nice 4 speed automatic, still shifts fine. The car has about 120K miles on it, but the motor and trans were swapped from a 940 turbo by the previous owner, I have no idea how many miles they really have on them, although the engine seems to have little wear.
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I'm JohnMc, and I approved this message.