I added brakes, the leading leaf spring attach points begin to tear out off the square tube frame when you do this, the metal is not strong enough to take the stress...it required another welded 2x2 square tube 3/16 thick and welded to the existing 1/8 2x2 frame underneath, welded parallel with the existing frame, then adjust the shackle length. The axle was special ordered, the width is not standard for 400.00.
I did this after a mishap when a tractor trailer did a u turn on Arizona highway 89A N.
I could not evade the semi even at 55 mph and had to leave the road to keep from going under the trailer across the road, the brake computer is under the passenger seat in my Nissan truck, the coaxial cable to the speed sensor (in differential) from the brake computer was severed when I left the road by large rocks now under the truck...My truck immediately lost the A.B.S control system, in this situation the brakes function on manual operator default control only. Had I had electric on the trailer my braking distance would have been greatly reduced, I lost the trailer tongue on the second impact with the outer barrier, the trailer went airborne into the trees when it dug in.
My wifes air bag discharged and the truck lost its passenger front tire. We were lucky, the truck driver felt horrible, we were all alive, property is replaceable, insurance was a pain in the rear though.
I added the trailer brakes after this incident.
The odds of the loss of the A.B.S. system at the same instant is rare...I did not think its was possible, I learned...In the cases where the perfect storm is hedging the bets against you a little over protection by anything reasonable is worth the money.
I always put money into brakes over the engine.