I had the same issue with my big block. With stop and go traffic my temp stayed around 195 with a 195 Tstat with one 1/8" hole, Be Cool 2row 1" tubes and twin electric fans I modded from an intrepid OEM fan assembly. At freeway speeds or when the car was making good power my temps with start to rise 210 ish over a long stretch. That's too hot for me honestly. I decided to go overkill and gain some engine bay clearance all at once so I found a griffin 2 row 1 1/2" tube and mounted it in front of the core support. I then modded a fan assembly out of an 2000 CL 500 Mercedes to fit behind the radiator core support where the original radiator was. I was just out last weekend and the car didn't get above 181. My issue was simply not having enough radiator perhaps that is your issue as well.
View attachment 1714938292
View attachment 1714938293
View attachment 1714938294
