1990 M47

Is there a way to check to see if the flywheel is in the correct position without pulling the transmission?

My shaky idle may be from the flywheel being improperly installed after a clutch change. At the time the clutch was done (by a non-Volvo mechanic friend, he's great with muscle cars though) the car had other "issues" that made it run poorly so it didn't raise a red flag at the time. Those issues are fixed and I cannot find anything else wrong. The car runs decently off idle and my MPG is within spec. Plugs have white ceramic but the threaded part is carboned up. Combustion chambers have a bunch of carbon in them (compression 190 all cylinders). Fuel pressure is good. Timing belt marks are all on the money.

A friend checked my timing with a timing light this weekend, the mark was WAY off the scale...near the alternator! Hard to say how many degrees the timing is off exactly, his guess was ~40 degrees. Having the timing off by this much leads me to believe the flywheel is improperly installed by one bolt (8 bolts, 360 degrees, 45 degrees per bolt). Does this make sense?

Anyhow, (again) is it possible to check for proper flywheel position without removing the tranny? There must be a mark that the crank sensor sees, BUT is it visible from the engine compartment...

Thanks,
Zuda