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Pictures might be good. How much of the brakes are being replaced? Shoes or more????
Airstreams built before the early 1960s have straight axles with leaf springs. Like most of the rest of the non-Air Stream trailers made by other companies today. I think the vendor for the brakes is HADCO. (I could be wrong on that)
You would need to know the brake drum size and the backing plate mounting arrangement. There may be numbers on the old parts or logos.
Ordering by year make and model will be fruitless.
I think ordering an axle is over kill. Is your brake guy, a trailer guy? These trailers are not like cars and trucks.
1966 Mercury Park Lane 4 DR Breezeway 410 4V, C-6, 2.80 - Streamless.
1966 Lincoln 4 door Convertible 462 4V 1971 Ford LTD Convertible 429 4V Phoenix ~ Yeah it's hot however it's a dry heat!