[ERA Chas]

The wheel / tire combo jumps out. Avons are great but heavy-take your choice. Trigos too.
To compare, my Billboards and magnesium Halibrands:
Wheels: F17.8# R19.7#
Tires F245-60, 18#'s R 295-50, 22#'s.
Combined F 36 R 42
Your best bet is race slicks like G-7's and maybe a bolt-on aluminum 2 piece race wheel. You can get bolt-on hubs for the IRS.
Good job weighing the Jag rear-I forgot to do mine. The newer ERA IRS is 50#'s lighter.
Boy, that warehouse you work in is pretty shabby...