Flex Plate for 360 Magnum Engine

@PowerWagon0322
You need to buy a stock, factory type flex plate for whatever year 5.9 Magnum you are getting from ATK. If you tell a person ordering parts that you want it for a 360, you may be confusing them...so call it what it is, a 5.9 Magnum engine. Yes, technically they are both 360 CI.
A 5.2 Magnum flex plate is different than a 5.9 flex plate because the 5.9 plate will have balancing weight welded to it. A 5.2 Magnum is internally balanced, so its flex plate needs no weights.
See if your transmission shop can return the torque converter they gave you and swap it for a neutral balanced 727 converter with no weights. You might be able to knock the welded-on weight off the one you have, but sometimes it cracks the converter and makes it leak.
Match up the new 5.9 Magnum flex plate to the converter you are going to use before you bolt it all together, so you can elongate 1 converter to flex plate bolt hole. Make it fit, mark the converter and the flex plate so you can line them up upon installation. Marking may not be necessary, but you will know it fits the first time!
Just to recap, you need a 5.9 Magnum flex plate, there are no weights required on any converter for a 5.9 Magnum, you will need to elongate one bolt hole to get the converter to bolt to the flex plate.
I hope this helped. :)