The SRT-8 published combined mpg is 18.4.
http://home.comcast.net/~300_C/p20.htm
Based on this table, the tax would be $2,600.
http://216.239.63.104/search?q=cach.../autos/guzzlertax.shtml+gas+guzzler+tax&hl=en
GAS GUZZLER TAX
Unadjusted MPG(combined)* Tax
at least 22.5 No tax
at least 21.5, but less than 22.5 $1000
at least 20.5, but less than 21.5 $1300
at least 19.5, but less than 20.5 $1700
at least 18.5, but less than 19.5 $2100
at least 17.5, but less than 18.5 $2600
at least 16.5, but less than 17.5 $3000
at least 15.5, but less than 16.5 $3700
at least 14.5, but less than 15.5 $4500
at least 13.5, but less than 14.5 $5400
at least 12.5, but less than 13.5 $6400
less than 12.5 $7700
Apparently the Gas Guzzler Tax paid by the manufacturer will be disclosed on the automobile's fuel economy label (the window sticker on new cars).
I think you have to pay the gas guzzler tax just like any other tax.
On this Pontiac website, the gas guzzler tax is extra.
http://www.pontiac.com/currentoffers/regional/index.jsp?year=2004®ion=we&brand=gto
Manufacturer's Suggested Retail Price. Tax, title, license, dealer fees, $1,000 gas guzzler tax and optional equipment are extra. Gas guzzler tax is required only with automatic transmission.