Do a search in this forum for 'rsw007'. He runs 13.00's with very minor engine mods (intake, bigger valves in stock heads, factory headers), and the big key for him seems to be his tranny mods (stall convertor, shift kit) and a tranny cooler to keep it healthy.
His car is more the exception than the rule, but you shouldn't have any trouble getting into the mid 13's with afformentioned mods with the 3.73's you're planning on as well.