I just bought a 98 Z28 roller. It still has the wiring harness and computer in it. The guy i bought it from just took motor, tranny, and driveshaft. I would like to put a LS1 back in it, but being on a budget i am thinking about a cast 5.3 or 6.0. For the fact they are cheapier and i would like to put boost to it after i get it going. So........ what would be the best 5.3 or 6.0? Would the 6.0 need a lot more modifying? Any help would be very helpful

 

The 5.3 is considerbly cheaper to buy as a whole engine. I saw one on ebay last week for $800+ shipping for the entire engine with everything on it including wiring harness (no comp though). Parts for both are marginally close unless you get a gen IV 6.0 on which the electronics tend to be slightly more expensive. Now when you say boost, what exactly do you mean? Also before you can really choose and engine what are your overall goals for the engine/car? I personally am building a 6L cast (lq9) but im starting from scratch...My reasoning was there are two things you cant replace in life: cubic inches or cubic dollars.
Anyway, goals and budget? Then we can help you decide!

 

that kind of swap is not hard at all..

id personally go with a 6.0, but thats personal preference, they make more power n/a...but to swap either one of them iron blocks in, youll need a ls1 oilpan, ls1 windage tray and pickup, and will need to drill a hole for the alternator mount. you will also need a ls1 intake mani. obviously..

all the electronics will plug right in, as they are the same part numbers as the ls1 had...i did this swap and was pretty much straight forward...

G.L. with your project

 

I'm not real big on making a lot of power right now. Just on a budget for now. I am going to buy a 5.3 tomorrow for $400 low miles. I have been looking around and saw that the bore on a 5.3 is 3.780 and to make a 5.7 with stock ls1 pistons I need to go to 3.898? Just making sure because I want to go to machine shop and get quote on boring and balancing.

 

It will be almost a direct swap. You will need f-body accs though, the truck ones will not work, and f-body oil pan and intake, and you need a Gen3 engine which means 24 tooth reluctor on the crank for the computer to run it. Mid 07 and up will be more of a pain/money to get working.

 

I would toss a 6.0 in it. I picked mine up my 2004 LQ4 complete harness and ecu with 13k on it for 250$ You will have to swap to a car intake and a front accessories though.