Gear ratio/tire size

Ok my duster 73/318/904/4 barrel /dual exhaust/8.25.has 2.45 rearend gears.plans for a rearend swap are in order.but for now I'm wondering how short of a tire I can install that will help out .it's a dog around town which is all I drive it.i don't even go on highway.im gonna put 410 gears in it.but wanna do something for now.i know a 195/45 r15 Is 21" tall and I think puts it at around 3.00 gearing.thoughts.?