4x10 Speaker Template?

[BAChevyMan]

Anyone have or can make me a template for the center 4x10 speaker slot on a 86 C20? I have a custom 6x9 box for the back, was going to put some 3.5's in the dash corners. Then run a under seat sub and a pair of 4 inch 200w in the center. But all I can seem to find is a dual 3.5's. And whereas I make the hole bigger... what if it makes ot to big? I am fine fabing my own bracket, I just mainly need the outline of the speaker and advice on how its mounted. It looks like most people send the screws up from under the dash, I just worry about sening it completely through the dash cover. Not sure what mounting screws to use.