I think you should bring to my shop and I can build you the bumper and reinforce your frame for you.
on a side note i would just cut the frame to the length you need. You should not go past the spring hangers unless you are planning on moving them. The frame is c shaped from the hangers back . i would just add a peice of square stock .25 wall with your reciever in the middle acroos the frame. maybe ad a few gussets. If done right you can make it flush with the end of the bed. Hard to explain i know. Just get down there and get creative or PM me and we can talk.
Good luck
CRS
