As far as the tank goes if ya can get it down a bit it may help. I've read here a couple times about lining up the tank with the carb but I honestly can't remember what the exact recommendation is. I gotta think that mounting the tank in the stock location would be ok but if you can drop it an inch or so, I would.
As for your mounting screws, I do NOT recommend wood screws. Use "T" locks epoxied to the back side of firewall and machine screws. (Allen head type) and beef the firewall area up good.
Wood screws simply will not hold up to the test of time.