Finned vs smooth brake drum

9 inch

finned drums 5 on 4 inch PCD

Repro Finned Rear Brake Drum, Spring, & Clip Set : SV1-VG FITS Chrysler Valiant | eBay

finned drums 5 on 4.5 inch PCD

Repro Finned Rear Brake Drum & Spring Set VH-CM FITS Chrysler Valiant | eBay

provided drum depth is ok these will fit. Mopar in stud spaceing and centre bore
9 incn US and canadian drums fit my aussie car so aussie drums should fit a US Canadian mexican derived car

i.e the stuff that ended up in spain as local production or CKD Kits via chrysler Europe in Belgium ie spanish dodge desoto fargo.

designed for Track Pack Pacer and Charger RT in Oz
part of the gear homologated for raceing in 1970-72

the best improvment to mopar brakeing in my view is disks on the front and work on bias, either narrower rear cylinders or an upgrade to later rear brakes to get rid of the 60s duo servo design.

taller tyres bigger rolling radius at the back also helps.

let the front disks do the job properly without having to back off becasue the rears locked up in an alarming way.
your experince may differ Bitumen/TarMac highway or Concrete highway tyres water and temperature play a part

Dave