I have a 67 440 that a rod let go and tore a big old divit in one rod journal. Thankfully it didn't hurt the block. I had another set of rods resized and the pistons hung on them. My question is, I have a cast 440 crank and I'm wondering if I can use it with the 67 pistons without a big difference in balance. I realize that the forged crank is internally balanced and the cast crank is externally balanced. I have both types of torque convertors. This is going in a truck and will probably never see 4500 rpm.

I'm assuming (for now) that they both used the basic LY rod. With your cast crank & dampener & torque converter for it, all that is left is the pistons. Do some searching & see if you can find out the weights for 67 pistons & the later ones. 67 440 pistons had a lower deck height (iirc) cuz of the CC heads but I would search & if needed for this HF has a gram scale for $9.99 & it is just as accurate as my deceased buddys' high dollar scale. once we know the nominal weight difference then we can see if it is "close enough" or if too heavy the rod can be lightened tho weighing rods is more difficult cuz you gotta get it horizontle & there is a bit to that.

For your purpose, slap it together and forget about it.

That's what I would do. For a truck engine I wouldn't worry about it. I have pulled apart some old engines with a 1/4" thick layer of carbon stuck to the pistons. That must affect the balance too yet they don't shake apart to pieces. Don't forget the cast cranks take a different damper as well.

Most stock 440 pistons are right around 858 grams. Pin heights vary. Balance should be close.

Two things, why did the rod fail?
The other is have you thought about repairing the hurt rod journal?
If not, why not
As far as using a externally balanced cast crank with a internally balance converter and crankshaft balancer why would you do that ?
Years and years ago I put a 1971 440 six pack rod motor short block together for a friend, his wifes car, who had a 1968 Charger that he wanted to replace the stock motor with the later motor, he reuse his heads and so on including the 1968 balancer. That motor shook around 2300 RPM bad enough to be noticeable, it never failed though
Are you feeling lucky NOT ME

I rebuilt the motor in my Dart 30 years ago.Bored it .030 and replaced the pistons with Mopar Performance ones at the time,I didn't have it balanced.That motor has a vibration that starts 2200rpm and is there all the way up.Don't skip on that,you will regret it later and it will be very costly to re-do

Typically I would have the rotating assembly balanced. I am doing a bucks down rebuild to make this truck run. I am not using the cast crank with the forged crank balancer and neutral convertor. I have a perfect cast crank with the proper harmonic balancer and weighted convertor. I bought this engine from a guy that said it had a knock. He said he had just replaced the timing chain and it started knocking. When I tore it down, I found a red shop rag sucked up into the oil pump pickup and number 8 rod had the bottom of the rod bent up with the rod bolts facing the other way and a quarter inch divit in the journal. I should say it must have had one heck of a knock! Yes I could probably have the crank fixed, but right now I am short on time and money. I would like to use the crank I have if possible. I have been trying to find the difference in weight between the 67 pistons and the later cast crank pistons, as yet I have had no luck.

Weigh one rod and piston of both types and go from there
I use a 25 lbs. postal scale for heavy parts like that and a Haus triple beam 2500 gram scale for lighter parts that may weigh under 2500 grams.
I saw a comment on here on a different post about Harbor Freight selling a small digital gram scale for $9.95 I'm not sure how heavy it will weigh but it would be better than nothing

11 lbs (5000 grams) $9.95 HF EDIT It was just as accurate as my buddys' very high dollar one. I'm sure it wouldn't have the longevity but I was (very) impressed.

Thanks RR. I have a HF 5 minutes from my house. For the price it's well worth getting. I will weigh the pistons and rods then post my results.

Just assemble it and run it. Chrysler balancing limits were so much larger than the Ford or GM limits because the engineers were saving a buck on something that didn't matter. If the public never complained about Mopar engine running rough, they were balanced well enough.
It's been done since the cast crank era began, the rods and pistons are close enough, the counterweights are for the different density of the cast iron and steel. So match the flywheel/converter/balancer with the crankshaft and run the sonofabuck.

R.

That has been my thought too. I have been in touch with a couple of piston manufacturers and they said that the pistons I've got are both considered stock replacements. RockAuto shows either piston available for use as a direct replacement. One has a compression height of 1.912, the other is 1.991 I don't think it will be a problem for what I'm going to use it for. I will post more when it's up and running.