Industrial Engines
5-8 hp= comet 30 series torque converter (thats the 'transmission')
8-18 hp= comet 40 series torque converter (thats the 'transmission')
only transmissions available commonly include the 'comet FNR gearbox (forward, neutral, reverse this is good for up to 16 hp, and the driven unit of the torque converter fits onto the shaft of the gearbox)
GY6/chineese scooter engines (150cc, 250cc)
these also use a transmission similiar to the comet, but it is built into the engine
these also use a FNR gearbox, they commonly come in 1500cc style, and 250cc style
Notice that all of the above transmissions are AUTOMATIC, and you can add reverse with a FNR gearbox,
Racing Mower Trans
some mower racers use a peerless transmission that is BUILT (you cant just buy a regular old peerless trans, but you can buy knock offs, and built transmissions) a built trans will hold up better, a regular mower trans will just crap out on you and shear stuff when the torque is applied.
The rest
different variations of quality/style clutches
$20 clutch, cheap crappy clutch good for smaller up to 7 hp engines
$50 clutch, some are good for 3/4" shaft.
80-$100 clutch, varying quality, but much better than the cheap $20 clutch,
$160++ most of these clutches are racing style disc clutches
ATV/UTV
no idea there.
