Looking for advice on a blueprint engine.

Heywodja said
First off this is not a Mopar, but I was hoping the engine GURUS could help me decide on which engine to purchase. Both are in the same HP range, although the 396 does have a couple more points of compression, which may not use pump gas. Both are built from the same new casting 350 block, and both are in the same price and HP range.

I am ordering a long block because I already hve an ignition and pla on using the performer RPM Airgap manifold.

The one I am leaning towards is this one, it is a 350 stroked to 396 with 6.0" rods and a 4.0in" bore. Forged crank, rods, and pistons.

GM SB Compatible 396 c.i. Engine - 491 HP - Long Block

Or

This one which is also a 350 stroked to 400ci" with a 4.125' bore and a 3.75" stroke also using a forged crank, forged rods, and forged pistons.

GM SB Compatible 400 c.i. Engine - 500 HP - Long Block

I am leaning towards the 396 because of the 6" rods, however I have no clue why because I am dumb as a box of rocks on the math of what works or does not work.
I may have read somewhere or picked up from conversations that a 6" rod is preferred.

They should just make one with 6.123 rods and a 4.040 bore and that would be easy, lol.

Thanks in advance!

Rod length can be like bringing up polytics or religion. Ask 5 guys and you are liable to get 9 answers.
Find the David Vizard Powertec 10 episode that discusses his cam LSA selection formula. There are a couple.
Now this will mess in a couple of guys Corn Flakes, bit DV determines LSA by his 128 formula; LSA = 128 - (cyl displacement ÷ (intake valve diameter × 0.91)). Now this is a starting point as there are things that require a little correction. The main is CR, a high CR requires 1° more LSA. A quick off the seat or higher ratio rockers may require 0.25° to 0.5° more LSA.DV states that testing on a Prostock engine with rods up to 1/2" different length only made maybe 10HP dfference. On a 1,000+ HP engine, that is within testing error range.
A longer rod will run slightly quieter due to less piston slap.
Look for another DV Powertec 10 youtube on running 14:1 CR. Octane of water is pretty much infinite. DV mentions a water injection system but there are others. Being you are in Texas, freezing is not a major concern, so running distilled water is an inexpensive option. Use a fair amount of water when vacuum drops. Small throttle opening is not prone to detonation. During phase change from liquid to gaseous state, water absorbs huge amounts of heat, cooling the combustion and preventing detonation. During this phase change, water expands 1,600×. This is how a steam engine functions, so that steam aids pushing the piston down. This would be much less expensive over the long term. If freezing temps are forecast, a gallon of methanol added to the water tank will keep it from freezing. May only need a quart. Add about 2% water soluble oil that machine shops use to help lube the pump and prevent corrosion.