Depends on business model of the shop.------Some will help and some see every boat owner as a " source of revenue "-----Up to the owner of the motor to find the answer.
Sorry----Up to you to do the research.-----Many places on line where you can look up the part numbers.------I have to rebuild a 1974 model 40 HP for the grandkids to learn to waterski.----More worth while.
The motor without the cowling does appear to have a different lower unit ( cooling water inlet ) than the long shaft motor.-----Take powerheads off and see if gasket between block and exhaust housing is the same.
I do not believe larger OMC motors were ever meant to run at 100:1 mix.----It was a brief exercise by the board room in the mid 1980's to run the 6 and 8 HP / and 9.9 to 30 HP on 100:1 mix