Trouble there is it has to be chrome moly and Tig welded. I had my Daytona (mild steel) updated to 7.50 back in 2008. My 74 duster is a 6.50 NHRA cert. chrome moly is crazy high in price now.
I believe Bonneville, the recommended is mild steel for the added weight. I reached out to a semi local NHRA inspector. See if he replies and go from there.
Fear is setting in that this is just a dumb dream. Just make it a fun car, then build/buy a ready built chassis and have it dedicated to this plan. This is plan B, and may be too late to make it good/safe enough at this point.