Oh man what a find, that's the one everyone dreams of finding, I don't think I could bring myself to cut it up either.
If you do a LS swap and a 2/4 spring drop you dont have to cut on it at all and I have a few recommendations.
If you get a Vortec you can relocate the AC compressor up top and since the stock truck exhaust manifolds will interfere with the frame you can buy TBSS stock or clone manifolds.
If you get a car LSx the AC compressor is already up top and you can run the stock manifolds.
It would be a good time to do a Vintage Air Surefit retrofit at the same time.
http://www.vintageair.com/
It would also be a good time to do CPP rear disk w/E brake.
CPP has a brand new sheet metal engine perch, this combined with their poly motor mount and LS swap engine mount plate (stock location) installation of the engine is a breeze.
You will also want to buy their tubular transmission crossmember and poly mount to complete the retrofit.
http://www.classicperform.com/
I am speaking from experience, as I recently did an LS swap into my truck and I went through a lot to figure out how to get it to work properly and I could have saved myself a lot of headaches had the new sheet metal engine perches been available when I started mine but fortunately when they came out and I went ahead and purchased them and they made the swap like pushing the easy button and I highly recommend them.
I also recommend PSI for your wiring harness, and PCM reprogram, the quality is excellent and also aids in making the swap super easy.
http://psiconversion.com/
If you need any advice at all on the LS swap please don't hessitate to contact me.
Good luck.