I am looking to buy a converter. How do I know what a dual ,small or large bolt pattern is so I can order the right one. I have 70 455 in a 69 GS o No:
Just buy a converter for the THM350/400. The flexplates are drilled for both bolt patterns in most cases.
New... MOST new flexplates are dual pattern. But you must ask for the dual pattern, otherwise the guy behind the counter will sell you what your cars has.