4 SPEED INTERCHANGE QUESTION

I do believe you can . If my memory serves me the bellhousing has two patterns for the trans that allows for either 3 or 4 speeds. Over 20 years ago I switched over to 4 spd from a factory 3 spd and used the same flywheel, clutch, bellhouse, throw bearing etc. Even the drive shaft. Trans and shifter were the only things swapped out. Again that is what I recall. This was on a factory 340 3 spd car. Others might chime in and refresh my memory.