Hey Gurus, I'm rebuilding a C39 Dynamo (generator), it has the tach gearbox extension. The drive pulley is 3 1/8" is diameter. I'm used to the 3 5/8". What's 3 1/8" application; Mini? Just like to know what I have and know it's been discussed before but couldn't find it archived. Thanks, Dave 59 :{) 59 MGA 1500 05 MCS Burlington WI