Fender welt/gasket ?

[Gun Runner 5]

I took a peek under the hood and between the number of bolts and the VERY limited workspace I don't envy your task.

 

[Senior]

The trick with these gaskets is to warm them up in a bucket of hot water which makes old or new more pliable. If either end is sticking out a small dab of a black flexible adhesive on one side of the gasket before its tighten up will normally sort that problem out. This job is best complete with 2 people, one holding gasket in place and the other tightening up bolts.

The same trick works well when refitting looms if you have a small container that you can direct warm air into to make more pliable.

Please note that I said warm up NOT heat up as you can cause damage with to much heat.

Hope this helps