Any FE experts in the house?

So, I was buying some 429/460 core engines from a guy last week, and he also had what he said was a 410 Mercury engine, so I bought that too, to replace the tired old 360 in my truck.  I've messed around with a few FE's, but they're really not my area of expertise. I took him at his word about what the engine was as he seemed like a straight shooter.

A little google research tells me 410's are basically just 390's with a 428 crankshaft.  Seems all the web experts like to tell everyone that all 410 and 428 engines are external balance only.  No hatchet weight on the front of this thing though, so I was thinking it was just a 390, but then I pulled the pan and found a "1U" 428 crankshaft.  Don't know the bore yet, but it's all stock - high mileage looking internals.  No reason to believe it's ever been taken apart.

Block and head casting numbers are 1966.  It has a 4-bbl "S" intake, also 1966, and it has the old Mercury valve covers.

I came across one guy online saying he had early 410 without the hatchet weight, and other people saying something about how only some 428's were externally balanced, depending on the type of connecting rods.

Anyone know for sure?  It's all going to come apart and be rebuilt/balanced anyhow, but I'm just curious about the history of this thing.

if i remember right the hatchet weight was only on the scj 428's since they had the heavier lemans rods and a diff center counterweight crank. p/n IUA and IUB cranks.
pass car 428's and cj's are ext. balance in the rear only and have reg smooth spacer .
the 410 has the 390 4.050 bore? and a 1U crank.it should have a ext balance flexplate and a plain spacer in the front.
there was another 428 crank it started with a C6 or C8 part#.

As has been said:

A 410 FE and a 428 FE use the same crankshaft except the "Super Cobra Jet" 428 engines.

They are all EXTERNALLY balanced but, except for that SCJ which uses a hatchet weight on the front, the others are REAR EXTERNAL ONLY and use a counter-weighted flywheel.

What Randy Said...

Thanks guys.

I can tell you they run great ! My mom had one factory in her 1967 Mercury, made that boat of a car fast ! Ran much stronger than a friends 390 car, no substitute for stroke & torque !