crank bolt issue

I'm having an issue almost exactly like the one in the thread (Rotor and alternator swap, is possible) I didn't want to hijack that thread. So please refer to that thread if you want to see pictures.

I have an 83 belt drive 750 twin. The 83 motor gave up a connecting rod bearing long ago. Twice I have had to replaced the motor in this bike. Once with a 79 which gave me 5 summers and finally started to develop a weak valve, and that was replaced with an 80 motor which gave me 3 seasons and popped a head gasket this season.

In both cases, I've just had to switch the clutch casing, alternator casing, and the output shaft casing, which allows me to continue using my belt drive and charging system. That is until I bought this oddball 77.

This spring my motor sprung its head gasket and started pumping oil right into the left bank (on my 3rd ride out, POUT!!). So I searched and searched my area and finally came across a 1977 B2 within driving range which I scooped up and was tickled pink about because I'd be on the road this year, and could fix my other motor when I had the time.

HOWEVER: it's almost the same situation as with the 650 in the other thread, except I'm having a flywheel issue rather than the single and 3 phase electrical problem.

Of course after testing the 77 the stator is shot and the field coil output is out of range also. (not worth replacing imo, crap I could buy a whole bike for the cost of the things.))

If it had been alright I'd just have just used the 77 harness on my machine and converted back to chain drive for the season and been a happy camper, but since they were trashed I thought. "Fine I'll just ditch it and put my flywheel on while I'm at the other casings."

That was until I looked in the manuals and pulled the flywheel bolts out of both motors, sigh... the older 77 is a 12mil bolt torqued to 50 ft lbs or so.. the newer flywheel is a 14mil bolt torqued to 100 to 120 ft lbs..

So my question is: Can I get another higher tensile 12mil bolt that will take the 120 ftlbs of torque needed so I can use my flywheel, OR am I going to be forced to have the bearing material cleaned off the crank from my 83 motor and put it in this 77 motor..?

I want to ride this season so I'll be replacing the head gasket and stupid little o-ring on the 80 motor that was in the bike but, this 77 motor is a good solid motor with 90 lbs in each cylinder with 1 kick and 100 lbs with 2 kicks, so I'd like to get it ready as a spare and get some future use out of it.