I JUST BOUGHT A 04 MUSTANG GT CONV NEED ADVICE FOR MORE HP

Yikes, no need to yell.

The stock bottom end can hold 400-425rwhp with no problem. Push to 450rwhp and it may be on borrowed time. Push above 450rwhp, you should start saving for a new bottom end for when you kick a rod through the side of your block.

Most of the companies that make aftermarket blowers can get you to the 400+rwhp levels and still be reliable on the stock bottom end. Just start calling to see what each one offers and recommends for your car and make a decision.

I would prefer a positive displacement style blower (like a kenne bell, whipple, ect) over a centrifigual style blower (like vortec). Both can take you to big power levels, but the positive displacements will have awsome torque from idle instead of having a hard charge at the upper rpms like a centrifugal does.

No matter what you choose, be sure to get something that's intercoolered. It adds a margin of saftey and extra power to boot.

You don't need to beef up the bottom end or do head work before adding a blower. However, the gains from head work or a better exhaust will be multilplied when combined with a blower. Just install the initial blower setup and then add exhaust or other modifications as you get bored with the power levels. If you want to push past 450rwhp then get a stronger bottom end.

^thats some really good advice Also subframes, since its a drop top, and swap the rear gear

first thing you should do is full length subframe connectors and gears for sure.

The 99-04 conv. have factory sub frame connectors,which seem to do a great job at that horsepower level(always room for improvement). torque box's are more an issue imho because of the extra wieght of a conv. I agree a pd blower would be the way to go with a conv. also,I know I made the right choice going with a KB. oh yeah and GEARS!

I'm making 427 to the wheels with an aftercooled Vortech SQ package.
The blower you choose depends on what you want to do with your stang. For burning tires on the street, with instant boost/torque, PD blower. If your power cravings are more track related, I would lean with centri. But that's my preference.