1971 K20 LS 5.3L Swap issue headers

[DWilbur]

I have installed my LS 5.3 L in to 1971 K20 4X4 truck and I'm having issue with the headers fitting Dough Throly THY 323. I talked to Dough Thorly tech prior to buying the headers to confirm that they will fit my application. they confirmed they fit. Well they don't even come close. I would like to use headers, does any one know what headers will fit. I have a Dirty Dingo motor mount installed. with 1987 bell housing with hydraulic clutch.