Is it possible to change the fuel filter housing on my 82 300d to a later 1985 300d type, the 82 takes a crush washer on the spin on i always forget to change.
Could enough air get into the system via this washer to cause a starting problem?

Yes, The newer Filter Housings are a is a direct swap.

I do not see how any Air could be pulled in from the Filter Housing because it is under pressure from the Fuel Supply/Lift Pump.

The Old Style Aluminum Bodied Hand Primers are one of the common sources of Air leaks (becaue of it being on the suction side of the Fuel Pump).
It is also cheap and easy to replace the Plastic Primary Filter and the 2 sections of Hose to eliminat them as a source of a Vacuum Leak. The Regular 5/16" Fuel Hose that will fit you can get from the Auto Parts store is rated for Diesel Fuel and out here is around $1.20 per foot.

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84 300D, 82 Volvo 244Gl Diesel

I swapped the lift pump with a newer out of a low mile 85,i did not use a new gasket, i saw what seemed like a thin gasket attached to the pump and tightened it, the new lift pump already had a newer style bosch primer.
The lower right 10mm bolt on the lift pump is almost impossible to get to either from top or bottom, is there a special super thin and bent wrench for this?

I think one of those stubby 10mm would work. If you use the Box end you might have to thin that.

I only had a little difficulty taking off the lower rear nut. I did not have a stubby wrench but I had a shorter than average length Wrench that I have had so long I don’t remember where it came from.

Another alternative is to buy a cheapie set of combination wrenches and cut/grind the 10mm so that it works.

It is also possible that one of the wrenches in an Ignition Wrench set might work because many of them are in 1/32" increments. There may be one close enough to 10mm to work.

I think I found the wrench I used and I did get at it from the top but I had removed the Fuel Inlet Hoses and Plastic Primary filter for more room.
The overall length of the wrench is 4-9/16"; I thinned the Box end so it was less than 1/4 inch thick. I also ground of some of the outside diameter of the box end in one area and the Box end is angled about 20 degrees.
If I recall correctly even this wrench could have been 1/4 inch+ shorter because I still had only a limited range of motion.

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84 300D, 82 Volvo 244Gl Diesel