I've got this old 8hp mtd lawn flite with a blown engine, I've got a replacement but I can't get the drive pulley assembly to slide off the crank shaft. I've removed the 5/8 bolt and the 7/16, sprayed plenty of liquid wrench on it and it still won't slide off.

You need a gear or pulley puller. Three jaw version is best. Must be large enough to hook jaws to rear rim of pulley.

Hi,
A product like Nut Buster does far better than the commonly available things like WD40, Liquid Wrench, etc.
Peace,
Clarke