Hello All,
Thought an update would be helpful for those faced with the same challenge.
In the end I swapped the '94 AW71L bell housing (w/crank sensor cut out), for the '88 AW71 bell housing (no crank sensor cut out). The time and expertise is not that much; ~45 minutes, basic tools, soft touch and CLEANLINESS!
You will require 3 Volvo parts (thanks to white855T for providing);
1239673 - pump housing to planetary gear housing O-ring
1340096 - oil seal for torque converter flange
6814812 - bell housing to transmission case O-ring
Make sure you THOROUGHLY clean the area around the pump housing bolts before removing them. Same story for the joint between the bell housing and the transmission case. Removing the bell housing from the planetary gear housing is a delicate operation as it is a VERY tight fit and wants to take the gear housing with it. Gentle tapping with a plastic / fiberglass or nylon hammer around the perimeter of the bell housing should see it start to move forward. Having someone or something keep the pump / planetary gear housing in place will save you the frustration of trying to line-up and reinstall the planetary gear housing.
Install the torque converter oil seal before installing the pump housing along with its new O-ring. Easier to do when it is apart. Take note as to where the original oil seal sits in the housing before installing the new one to ensure it will sit in the correct location. Don't forget to remove the old and add new Silicone sealant to the pump housing bolts as required. Some of the tapped holes are exposed to ATF. Torque all bolts to spec. Go to;
http://www.volvotips.com/
On the right side of the page are the available service manuals. Go to the drive train section for the correct torque specifications.
Check the bell housing and planetary gear housing for any dirt or debris. Clean thoroughly with brake clean and a link free cloth. Install the new bell housing O-ring and thoroughly lubricate the planetary gear housing - it is a VERY tight fit and sliding it back on requires all the assistance you can give it.
Ensure the bell housing is square to the transmission case as well as lined up with the bolt holes before trying to slide it on. Tapping with a hammer is risky as you can not easily control if the housing remains square to the transmission case. We found that setting the bell housing on a piece of plywood on a concrete floor, having one person lower the transmission case onto the bell housing while the other ensures everything is aligned, works well. You can then use the weight of the transmission to drive it into the bell housing. Only lift it up a few centimeters before letting it hit the plywood squarely. Have your helper monitor movement - the force required when 'hitting the floor' will be dictated by the amount of bell housing movement. Go slowly and carefully - the bell housing will seat eventually. As it approaches the transmission case, keep checking the bolt hole alignment and make corrections as required. In my case we had to do some 'GENTLE crowbar leveraging and hammer tapping' to fine tune the bolt hole alignment. Torque all bolts to spec - see link above for where to find this info.
After installing the '88 AW71 and filling with fresh ATF (I prefer Dexron IIIH [final version of this ATF type]), I took the 940 for a 70km test drive. Despite only knowing the mileage and no service history of the AW71 (188K km), it proved to work exceptionally well, smooth but firm shifts, no unwanted noises and no leaks. Definitive improvement over the original (~350K km). Not having a lock-up torque converter will take some getting used to but I recently swapped the 4.10 rear axle for a 3.73 so the increase in highway RPM will be minimal.
Hope it helps. If you have any questions, please let me know,