Motobecane Gas Strut Spring Mod
The gas strut mounts to the exhaust bracket with a rod end, and to the stock center stand hole with a ball stud mount.
The gas strut weight is 50lbs mcmaster# 9416K11, the rod end is 59935K72, rear mount is 9424K23 on a 9512K73 ball stud.
The gas strut and all related mounting hardware costs a little over $20 shipped. And Mcmaster ships faster than Benji on a good day. Plus, you can buy porting tools, welding supplies, hardware, and raw materials from Mcmaster too. (Oh, and the gates AX29/30 belt for your moby for less than $10) The Doppler Spring costs almost $100 shipped, and it's variously out of stock.
The gas strut has a Very linear spring rate, acts as a Damper instead of a resonator, it's lighter, comes in a bunch of different weight values, and (with the stainless ball mount) dismounts without tools for easy engine removal. Plus, it is pre-loaded at the '0' travel position, which keeps you in 'First' gear longer.
Plus I think it looks way more Modern and 'Racey' compared to the big goofy trap spring.
More info here 
Credit goes to Max Johnson (motodrachen)