What's your greatest/favorite Grassroots modification?

Instead of purchasing an overpriced used Civic subframe, I cut the bracket and welded a square piece to the rest of the bracket. I cut the integrated nut off and just put it in place and accidentally had it big enough to wedge it against the bracket so it can be tightened without holding it.

First thing that broke when I bought my wife a 1968 Triumph Tr-250 25 or more years ago was the ignition switch. Went over to the local auto parts store and Robert (one of the owners) says "no way to get one of those fast, but it looks just like a Ford 8N tractor switch. $5 part. I take one home. Fit perfect, works perfect. Sold the car this year with the switch still in place and working.

I will just leave this here:

Best mod ever to my 924s

MJLJr

97 contour EDIS, coil and mounting bracket's

1994 Mustang V6 plug wires

72 tooth steel gear from McMaster car

323 GTX struts are NLA. So I got a set of take-off Protege5 struts, did a bit of drilling and welding (yes, I welded on the shock body) and put them in the GTX. Worked beautifully, just the right damping.

Best bang for the buck was this morning. I made a brand new 2016 Miata 1.4 seconds faster around our track using two HF tape measures, two pieces of aluminum plate with slots in them, a cellphone with a free angle finder app and a handful of wrenches. Used all that to set the front camber and toe in the pits.

The MR2 electro-hydraulic p/s system is my favorite. Used to have a variable resistor to control boost until I fried it with moisture.

I also have quite a few homemade chassis braces made from scrap steel and heim joints, converted a used MINI radiator fan to ditch my mechanical, and have done the McMaster Carr poly-urethane solid mounts too.

Homemade vented hood and splitter-

Mine was making diamond-plate aluminum half-doors for my Samurai by tracing my regular doors onto the aluminum then turning a circular saw blade so it runs backward to cut 'em out.

I spaced them out with blocks of cutting board that I traced out to match the stock hinges.