Thinking about a swap...

I have a 97Chevy K1500 Z-71 with the 5.7L.  I am thinking about trying to swap a 5.3L with a new trans into the truck since the motor is getting worn out.  I pull a 25 foot camper and other trailers on an almost weekly basis.  I don't really want to spend the money for a new truck right now and I have found several complete driveline setups for under $4000 with very low miles.  The only thing I am not sure of is the wiring?  Anybody know anything about this at all?  Thanks for your help in advance.  

I would rate a 5.7 Vortec 350 and better tow motor than a 5.3 any day regardless of higher HP rating or 5.3. I would suggest that you rebuild or find another VorTec 350 to bolt in and regear axles with 4.10 or 4.56 gears (depending on tire size) because properly geared a 5.7 can move a lot more weight than a 25 foot trailer. It is axle ratios that make or break a tow vehicle.  

I have been tossing that idea around as well.  I have been looking into rebuilding my engine or dropping the cash on a new one.  Either way I don't want to do anything without reworking the trans also, so that factors in a little.  Thanks for your suggestions and I will let you know what I come up with.  

i would go with the 5.7 seeing as my dad has it and a 4l60e and pulls a 33ft camper at almost 9thousands pounds occasionally, he needs a regear but it just takes a sec to get up to speed.other than that, it actually does great.  

Thanks for the help, but I came across a deal I couldn't refuse on a 2003 Dodge Ram 2500.