"Boxing" a frame in & a couple other ?'s

Well as some of you may know I did the v6 v8 swap and most of the original suspension is still on the car. It actually does ride very smooth with those v6 springs, but I've heard people talking about "boxing" the car frame so it doesn't flex on take offs. I'm guessing that my engine doesn't put out a whole lot o power at the moment. After some rides with friend's in their cars and knowing their numbers I've got a rough estimate that I'm putting out 300-350 hp and torque. I plan to do more in the future, but I'd rather stiffen up the frame now so I'm not paying for it later. What do I have to do to actually "Box" a frame in. I'm a pretty good welder so welding frame connectors(if that's what I have to do) in isn't a big deal, I was just curious if there is anything else involved.

Also, I know that you truly don't know the best rpm to set a limiter at until you run your car through a dyno, but I won't be doing that for a while, and I'll be buying a good rpm limiter probably before I run the dyno. What's a good rpm limiter to invest in and what's a reasonable rpm to set the limiter to before dynoing?

There is no frame to "box in". The best you can do is install subframe connectors.

Install a wonder bar (also known as steering brace) and box your rear lower arm or get an aftermarket. Try checking on Ebay for some of the parts.

I have been looking at the wonder bars. If I got the wonder bar for the steering would a strut tower brace help or would the 2 together just be overkill? And I'm assuming by boxing the rear you mean putting a stronger panhard bar on there?

Wonder bar and a STB isn't overkill, I have both on my car.

Here is a picture of a semi-boxed control arm
http://i11.ebayimg.com/03/i/00/8b/a7/c5_1_s.JPG
You could box your panhard bar as well or go aftermarket. The torque arm (attached from your tranny to your differential) could also be replaced with an aftermarket replacement. If you are short on $$$, I would go with the SFC's for your car.

With those numbers gets the sfcs to tie the weak 3rd gen chassis. box in your LCAs. get a wonder brace and STB. Last get the torque arm and panhard. Then worry about how long your rear end and tranny are going to last. Dont put a tire under it that will hook either.