Hot Rods anybody installing wood in 36 chevy std car ??

i have been copying some old wood in my 36 std 2 dr car getting ready to reinstall -should i use anything behind the wood ? i have used por 15 already ! maybe some urethane ?? to fill some gaps ? anybody got any pics of there installs ??

 

i have found strips of tar paper used behind the wood. it would insulate against any squeaks. duck tape or electrical tape would work also and last for years

 

im thinking maybe some "urethene" ?maybe the panel glueing stuff ? BUT if the body is not exactly assembled right ? it might hold it out of square ? anyway i will probably varnish or finish the wood somehow -before installing! at least por-15 -the area??thanks for any ideas !!