My trailer uses D1 frt spindles and hubs minus discs, but fabricated a "diff" that is essentially just a 3" steel tube axle with 8mm thick end plates much like the spindle mounts on a diff. Mounted on S2 leaf springs and shocks with RR steel rims.
The frame was a modified boat trailer that had a breakback and towed a 15ft tinnie. Changed it a little bit and added a Hilux single cab well body tub.
I think you might find the chassis and diff will add an enormous amount of weight overall and probably isnt needed.
Looks good though! I am looking for a SI, 2 or 3 tub to put on in place of the Rollux one i have now. Kind of keeps the theme going....!

