Hope I can help,

Volvo went to the M40 gearbox for the 1961 model year. Before up to 1960 they used the M4 series gearbox. The problem you have is the bellhousing. The bolts location on these early gearboxes which includes the 1961 volvo cars are in a different location than the later b18 engine cars transmission. So you will have a difficult time putting a later gearbox on your B16 engine. You now have a better upgrade than most B16 owners in that you have much improved transmission than the M4 and M3 transmission. However if you are replacing with a b18 or B20 engine you can use your later trans and bellhousing. Also the PV series cars have a different location of the speedo drive on ther rear housing of the transmission than the 122 series in that they exit the car more down than the 122s because the 544 has much less space than the 122 tunnel. You really need to use a 544 transmission for there not to be any motifications needed. HOpe this helps, john erik sandlund Have owned over 75 volvos and at least 6 PV´s