any good online guides to tearing apart a stock 700r4 and making it handle more HP?

Get an ATSG Manual. I have some if you want to buy one. I usually tell people to get a Helms service manual, but after looking through the ATSG manual, it looks like alot of the pictures and info was taken right from the Helms, so you'll save lots of money.

There's also the GM Transmission Overhaul book, made by Haynes. (Usually found at Pep Boys; I think you can find them online thru google.com ). It gives a photo-by-photo rebuild of the 700r4.

I also have the ATSG manual and the Helms GM Service Manual. I bought the ATSG after I had the GM/Helms book for years, only good bonus about the ATSG is that it lists GM's updates to the trans design in the back. Gives such info as new accumulator piston design and new valves and etc... the GM/Helms book only covers what happened for your year of car; it doesn't go into any "later year" fixes/updates.

I paid $20 for my ATSG book from http://www.naparts.com . You might have to call them; last time I checked, their website was pretty cheesy.

The books mentioned above are very good, and so are Technical Videos. The ATSG is printed on a lot thicker paper than the Helm
manuals, which makes it a much better manual to work from. I
bought my ATSG from Napa Auto Parts for about $20. I like the
rebuild kits from www.naparts.com (transtar) because they are
very complete and the price is good.

how much stronger could i possibly hope to make my r4 if i decided to try and rebuilt it?

Go to https://www.pro-built.net/index.cfm?...ct&productid=5 this will give you the best performance rebuild kit out there.