It just seems like so much work for a little gain. Why don't you mini tub it, move the springs inboard and use a housing floater instead of the coil over shocks. I don't think you can keep the the stock fuel tank and put coil overs on it too.
If he's going ladder bar he should have a floating axle anyways.The axle needs to be able to move somewhat side to side and back and forth. Ladder bar setup pretty well requires him to float it.
Heres what sold me on the caltracs and minitub setup.
The ladder bar system will add more weight. You will need a cross member welded ahead of the lb to locate the fronts of the bars. There are multiple thick plates to weld to the axle,as well as welding and more metal for the floating axle.
Then you have to work out the exhaust around it.And it will probably get more complex with more mods like inboard springs. Plus the ride with a ladder bar will be stiffer.There may also be ground clearance issues.Look out for speedbumps lol!
Ladder bars are proven hi h.p traction makers. But it seems to me that it's also old heavy technology. As a novelty idea or maybe just so you can say you did it yes it's kinda cool.
I personally would go with it if it was a dedicated race car