Wouldn't you be better off with a lsx427 than ls7 short block.much stronger

If boosting is in your future, then an iron 427 is the way to go. The weak link of an ls7 is the cylinder wall/ block support gets thinner, due to the larger bore size. I would not boost a stock GM ls7 block, but I'm not sure the OP wants to boost this engine.
Some of the early ls7's had valve issues, but that's not an issue with the mast black label heads.

Excellent feedback guys, I appreciate it......... all roads are pointing to LS7 as that is what I have always wanted. So its time to do the right thing and pony up for the LS7 versus the LS3 even though I know the LS3 will suffice. Now I wont worry about kicking myself and not getting what i wanted.

No boosting for me, straight up motor.......

thanks for all the input! :gitrdun:

We can build you a 427 with LS3 heads that will make the same power as the Mast LS7. It will be a dry sump though since that is the way we build them for durability reasons. I've been racing mine for 3 years and have never had any leak problems. We don't list any of our engine packages on our site but currently have a 600 hp, 650 hp package, and we are currently testing a 700+ hp package that will be going in my car shortly. Our horsepower numbers are with a mechanical water pump and accessories so they are real world as they would be in the car. PM me if you want more info. http://www.kurturbanperformance.com/

Kurt, I'm building an LS7 with LS3 heads because I'm using a Kenne Bell supercharger and that's what manifold it uses. But, as the OP stated, he isn't going to supercharge his engine. So, my question is, wht reason or why the LS3 heads instead of the LS7 heads on an LS7? Now, I do know, essentially that all 427's aren't LS7's, but I'm just curious as the OP stated he was leaning towards an LS7.

This isn't Kurt (I'm Tim) but I work with him daily. The reason for the LS3 heads is... there are far more intake manifold options out there for LS3 heads should someone want to run something different vs the vary limited choices for LS7 heads.

Thanks Tim. I now see your name "Tim" in your signature. Hahah!! I just wanted to know becuase I see alot of people using LS3 heads on 427. Can you pm me a cell or contact # so I can call you about some options?

Saw this thread good luck with you choice Im sure you will get a killer motor no matter which way you go.

check out our street and show series line up:
http://www.gashufferhotrods.com/category-s/1817.htm

We got both options for ya!:thumbsup:

Dasilva motorsport built a Z06 with a charger and a stock intake manifold, now it did have a cam swap and some head work but it put just shy of 1000 hp down at the wheels. They are the LS gurus lol. They're doing my motor for me I was told to expect 630-650 then got called a ***** for so little power lol