I'm not trying to tell you how to mod your car because to each their own, and I know every situation is different. However, you do know that if you choose to go LT's down the road that the Y-pipe you will spend x amount of money on to put on your stock manifolds will be useless. Why not wait and get a set of LT's and a matching Y later when you have the money to do it "right" the first time.
I only say that because you may just be looking for better sound or so forth and in that case go for it, but if your looking for gains you will be sorely disappointed. This is all IMO though.
Plus, if expense is a problem, why not go with pacesetter LT's and a texas speed ory (the pacesetter fits like junk from previous experience, they may have fixed it idk). Just my $.02 though.