What is the difference between the heater channels and what models would be the same as a 1957 oval?

Any help much appreciated
Cheers jamie

I'm not an expert but ive replaced a few of these others can correct me if i'm wrong. Pretty much ovals mid 53 to mid 55 with ribbed doors the heater channels have a oval shapped hole in foot well with a mesh insert. later ovals 56 on have vertical slots. then the 60's models had a little slide that covered the slots. most heater channels will fit but when you order just ask for 6v beetle.Most after market won't have any holes or slots so you will have to cut and shut from your old channels.
I would suggest you get the lower a pillars as well as there probably got rust in them. There are 2 different types of these as well cheap shit ones with one hole for lower door hinge bolts and cost about $25 these are incorrect for oval. or the better option is the one from Das Resto Parts about $64 but made from quality steel and worth every cent and have the correct 2 holes.
Hope this help you

handy info, VDU.88A