Rubber floor mat from a different truck to cover whole floor and firewall

[BigSix]

Has anyone ordered a different floor mat than the ones made for our trucks? I believe the ones made for our trucks don't cover the firewall. I was hoping to have a thick, insulated carpet or mat that went from the firewall down to behind the bench. I feel like the one I bought for my 1991 Ram would work but I am not sure how I would fasten it to the firewall section above the transmission hump. Any ideas on how to get complete coverage of the firewall/floor in one piece are welcome. Also, I have my sound insulation pad holes welded up so I cannot use those clip any longer. Would rather have a fully interior solution. I have a heat gun.