1965 273 2 bbl engine.

I am looking to install a 4 bbl intake to replace the 2 bbl. and also wanted to do just a basic rebuild with a mild cam, But I am having trouble finding parts that will fit. everything I have found is for 318,340,360
I've read that 64-65 273 engines are hard to find parts for, but I was wondering if anyone has found a good place to order parts from. This is the original engine for the car and would like to use if possible. Thanks