Converter- 67 273/904

the early 904's had a smaller input with 18 splines and the hub for the torque converter was smaller as well. so the converter is specific to 67 and down units. fwiw the 68 and later have 27 splines, so at least you'll know what not to look for.

the market for high performance/high stall early converters is quite small, so it's highly unlikely to find anything off the shelf that'll be a correct match for your particular set up-- although you *might* find something close.

most have theirs rebuilt to spec locally or have a company build one out for them. PTC and pro torque are highly regarded as is PACT Performance Automotive Transmission Center

at any rate, i'd 100% grab the numbers off the pan rail and verify what you have before ordering up parts.