Cost was about $200 for everything...got the bike from a Pawn shop,pretty much unridden.
Rear extensions are just plate steel from Tractor Supply.I just get the same thickness the orig. dropouts are.Some are 1/8...some 3/16.I don't like how short the wheelbase is stock,and I motorize some bikes,so they are more stable at speed.The setback also clears the way for running the big Flame,or Fat Frank tires.They will fit on the front springer fine too.I have already done the same model bike with 26x3 Kenda Flames front/rear.
Cut some 3" wide strips of cardboard...the width of the plate,and about a foot long.Take the rear wheel off and lay the bike on it's side...after removing crank,seat and handle bars so it will lay flat.Position the rear wheel where you want it.You can build in a drop by moving the axle upward some.Measure rear axle to orig. axle slot.Hole punch 3/8 in cardboard for axle holes.Attach to bike and trace outline of stock dropouts and all holes.I use the 2 fender mount 6mm threaded holes for extra strength.Some dropouts will not have the hole in front of the axle slot for the 4th bolt.I use 8mm buttonhead stainless bolts,locknuts and washers.Fender washers on inside to cover the area better.
If you want to save yourself some time,fit the chain before you finalize the dropout extension...you will need two because of the extra length.I do not have slots for adjustment on mine.It's a stronger assembly if no movement is allowed,and VERY important for sproket alignment on the motorized version.
This is one I sold in Feb. You can see the dropouts on it.