You might be the only other LS4 owner I have talked to that has that plug configuration... and I've been at this since '97. They are for external coolers, sumps etc. But the best way to find out if it is a 4 bolt is to pull the pan.The answer I have been able to come up with is this: Chevy ran out of LS4 blocks for the 73 model year production cars. They pulled blocks destined for the racing program, which were milled for 4 bolt caps and external oilers. They were built to stock LS4 specs, just with 4 bolt caps.
Other 454 blocks for 73 came with 4 bolt caps, but they went into trucks, and some replacement blocks for that year had a CE suffix code. Look on the driver side of the block above the bell housing mount. If it is original the casting # will be 3999289. This block was used from 72-75, but only in 73-74 for corvettes. The date code is important and is located on the same spot on the opposite side of the block. It is in code, a letter and 3 numbers. The letter signifies month (A=Jan, B=Feb etc,) 1st number Date, last 2 year. Mine is K172 (Nov 1 1972). This will help you date the engine.
Is this a numbers matching car? You didn't say in your original post. That number is on the stamp pad in front of the passenger side head, that number should have a CWM suffix code (454/4spd), and correspond with your VIN number.
I don't mean to write a book here... but have you found the tank sticker on top of the gas tank, or did you get any original documentation for this car?
Let me know what you find out.
Later,
Wedge
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I will definitely look for all of that in the AM. Yeah, it's a numbers matching car. I guess I got a better deal than I thought. The owner didn't know to much about Vettes, except that he couldn't sell it for the life of him, because nobody wanted an all-manual car with no AC. lol He hadn't done any internet advertising, just local paper. Maybe if he had, he would have realized what he had. I don't want to say what I paid, but even if it were a non-matching numbers mutt with a basic 2 bolt 454, I still paid a LOT less than I should have.

 

I'm turnin blue here! What have you found out... 2 bolt caps or 4???? The wait is killin' me... Let me know when you get the time...
Later
Wedge
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If that baby is an original 454 car i would not modify anything and would keep it origianl. of course that is if it hasnt been heavily modified already.

 

Not sure if this applies to big blocks but four bolt small blocks used to have an eight inch harmonic balancer.

 

I got a question for you..... what motor is actually stronger??? a 2 bolt main or a 4 bolt main???

 

Def a 4 bolt. The journals are a lot stronger, allowing you to build to higher compression, and withstand higher revs and torque. I wouldn't trust a 2 bolt to hold together, when goin' over around 450 hp. Go 4 bolt, and you can really pump the sucka up without much fear of blowing the bottom right out of the block.

 

Dave pretty much hits the nail on the head. 'Nuff said!
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hmmmm.... trick questionlet share with you why a two bolt main is stronger

uh-hum: A four bolt main is much weaker in the webbing area(where the main caps bolt in)due to GM drilling the outer holes too deep. You will get less core shift and main cap walking if you use splayed bolts on a two bolt main.

Sooo what is the strongest combo you ask??? a two bolt main converted to a four bolt with outer splayed bolts is the answer, trust me on this one 2 bolt is good to 6800RPM and about 500HPwith some ARP bolts.

P.S. This is a tryed and true statement. time...and time....and time again

 

P.S./P.S. most people will not ever be able to use the HP an two bolt main can put out.

Street/Strip= two bolt main for up to 380HP@ 6000 RPM/nice ARP set up 500HP@6800RPMwith balance/SAFE!!!

DRAG ONLY= two bolt converted to a four bolt with outer splayed bolts and 'hardened' water jackets is a 'cheaper' 1000+HP bottom end for drag use.