What timing cover are you using with a 7.3 inch damper

Mate I have been into mopar for the past 50 odd years in Australia back in late 70’s I built a turboed 440 phoenix ( first car done by Phil ward),then stuck mainly to stock except for my k16 cl charger.
I know 273 were the only motor here to get the timing cover without the timing marks moulded into the cover which means to get that balancer to work you would likely need an early cover with that balancer,.
EDITED
I’m throwing an edit in here I did finally find this supplier in Melbourne they seem to do a lot for chev and ford as well as the ones for mopar they all are able to have the weights placed on or taken off, I see they are modular iron so will be stronger.
Are you certain they have not accidentally sent you a big block balancer as they do not mention measurements on the mopar ones but do mention upto 8 inch on the chev ones I would be double checking that with them

I looked up that brand pro street and all I can find under that name is 2 automotive workshops one in castle hill and the other in newscastle, are you sure it is not another brands balancer modified or sold for mopar but better suited to ford or gm.
Could you also give me the rationale behind a big balancer like that, does it have to do with needing extra mass for what I guess is a stretched 360 out to your 410 cu in
I know $$$ is crap but that is part of playing with cars you never get your money back on them, mine I bought everything back in 2012 when we were on parity and the bill from summit with shipping and gst was pretty high, not to mention all the things that were bought here for it.

These guys are not questioning your ability I’m sure the pictures of the timing covers are showing you what the factory put out from the start of the la small block through to the last gen3 as in the 300C etc