Over the years I have seen some flimsy below the bumper bolt-ons, but I wouldn't trust them with a 1,500lb-plus PUP tugging on them. Also, anything other than the hitch ball mounted on the bumper platform reduces the weight carrying load specified by the TV manufacture.
IMO, a frame mounted receiver is the way to go. Don't know what make your new truck is, but a new receiver can be had for around 200 bucks, or less.
Depending on how much higher your new truck is, you could look into the feasibility of going to longer shackles on the PUP leaf springs (raise the PUP), but it may be easier going the TV receiver route.
2016 GM 2500HD 6.0L/4.10
2005 Jayco Eagle 278FBS
Reese HP Dual Cam
Putnam Class V