03 5.3 into 1990 C1500 2wd Pickup

okay i have a 1990 chevorlet silverado that has an old worn out 5.7 tbi motor in it.
i recently bought a 2003 5.3 motor complete with all accessories and wiring harness and computer. i am wanting to keep my 700r4 trans and run it cause i love that transmission. they are so easy to rebuild. my problem is i am completely lost when it comes to wiring anything and i cant seem to find the motor mounts anywhere to fit that motor in my truck. any info or clues on how to fix the harness or anywhere i could get one would be greatly appreciated

OBS to LSX sticky This should answer a lot of your questions.

4l60-65 have same guts as 700r4. And less valvebody problems to deal with.

I used these, http://carshop.carshopinc.com/produc...id/74328/LS1GM, but now there are a lot more available. These are gaining in popularity, http://dirtydingo.com/store/Dirty-Di...323/index.html
Or look here, lots more. google search ls1 engine adapters
Also, just go ahead and run the 60e or 80e it'll just make things easier.
Call them for your harness and pcm tuning. http://www.nelsonperformance.com/

Thank you all I will check all this stuff out and get back to everyone like I said thank you so much