I agree with the 13 inch rims and the 8-10" widths. When you are looking for tires, I think you should look at the Hoosier R25 compound as it is soft enough to build some heat with what should be a light car in a Solo environment. The 13 inch rims should give you plenty of slicks to choose from. Not sure if the R25's would be too soft for TT's. Where are you located Nick? There are some strong running EM cars here in the northeast.
Emod is the pinnacle Solo class for production based cars. If you look on SCCA's (www.scca.org) site you can download the 2008 Solo rulebook in PDF format and there you will find the Emod rules. You will see that many, many modifications are allowed. If you are the creative engineering type and are working with a production based car, Emod should be a fun class to play in.
Joe Gonzalez
1979 Legrand DSR- B Mod
Gilbertsville, NY