What size tires can/should I get for my 99 Ram 1500 Sport?

I have a 1999 Dodge Ram 1500 V8 4x4 Sport and its about that time that
I change the tires (They are more like racing slicks at this point). I
was wondering what is the biggest tires I can get for the back and the
smallest I can get for the front with out effecting the performance too
much. If this stupid stop me now and let me know, but I got one of
those nice red ones and the previous owner put on this sticker (I think
its called a tear) that makes it that much cooler and everytime I look
at it, I think that it would look even better if it was slanted (rear
up front low). Now currently the tires and rims are stock, new rims
would be cool, but I don't won't to spend that much money. Raising the
back would give the effect I want also, but I know nothing about that,
or even how much it costs. So, I thought that the cheapest way to get
my desired effect would be to put bigger tires in the back and put
smaller or original size tires in the front. I believe I currently have
16 inch alloy rims.

Now I am REALLY cheap, normally I would just get my tires from Wal-mart
or Sam's club (and I wouldn't mind doing that if I can) I checked the
prices at Wal-mart and to replace my tires right now I think it was
$380.00. I really would love to see my car as I like I described, but I
would want to go over $600-$700 (i also need that to include the price
of the tires if I dont go that route).

I mainly use this truck for highway driving, but I also use the bed
alot to move big stuff and I hardly every go off road. The only times I
go off road is when I drive over the sidewalk cause there is too much
traffic (and I don't want to lose the abillity to do that). Even though
I don't really go off road, I still want the abillity to do that (so I
can't have super small tires).
Thanks in advance for your help,

Nick