replaced the center bumper filler on my 74 roadrunner with repro.having trouble keeping it stright it wants to fall off. the repros. dont have metal strip in them to keep them stiff, anyone had same problem what can be done to hold on properly. thanks

Beings I have no idea what it looks like, maybe glue on a piece of metal on the inside out of sight? So that would be just a guess.

I`m not sure about the your car but on the center filler on my volare I made a metal backing piece that I screwed under the filler to keep it from sagging. Can you remove the metal strips on your old filler and put them on the new one?

this strips are hens teeth , you would be better to modify the bumper brackets and suck the bumpers in to avoid this rubber strip .
I dont remember , im pretty sure this can be done on a 73/4

i killed myself looking for them 10/12 years ago , I restored mine , and someone told me I could have drawn in the bumpers .

I think its feasible . Unless you gotta be show room stock ,

The original metal insert usually IS the problem...It will rust and come loose then the filler distorts and it's all over for the piece...
I wouldn't miss the opportunity to call the manufacturer and ask what they had in mind to hold their part on the car...If it doesn't work then you paid too much no matter what the cost..

With that being said..You can buy some windlace like this stuff windlass that has the metal insert and install it inside your "new" filler..That's your only real way out without creating a mess IMO..