I've been experimenting with ATV shocks.
I really like the Yamaha Moto 100 shocks for pavement. Just about stock length.
http://www.ebay.com/itm/1987-Yamaha-...1583cc&vxp=mtr
They are too soft for off road use and adults though. They would be very good shocks for lighter kids.
I'm waiting to install the Yamaha Moto 250 shocks.
http://www.ebay.com/itm/Yamaha-Moto-...ebba1a&vxp=mtr
I think they will be pretty good. Not too stiff, but much stiffer than the 100 shocks. Also around stock length. Might be a good choice for an adult driven Yerf.
Hard to tell length in pics, so Email the sellers on Ebay. Most will get back to you with length.