The largest drop in without using a .020" over gasket is a 181/218 Custom. More duration has more effect on piston to valve issues that more lift does. If you have a .020" over gasket i can fit a 206/224 all out race grind if I degree it in just right. I would need to know if it was in a 12v or 24v, what the head gasket thickness was and if your block or head has been decked. After that I would need to get it cut and then I could set it up on an engine like yours in my shop. It would be turn key with no degreeing for you. Give me a shout at the shop if you have any technical questions about your setup.
Zach Hamilton