Isky 264 Mega in a 400

It should make your tires go up in smoke pretty easy. Is it a 108 lsa ?

Yep, it's a 108 lsa cam.

Quite good idle quality. Not dead smooth, but not rough either. Used with a TQ carb.

Idle quality would be what I call "noticeable".

Awesome! I don't want a rowdy idle with crappy vacuum on this engine. I still had some doubts about idle quality since I wasn't able to find a video on youtube of that cam idling. Everyone seems to go for the 270 Mega or bigger, and by that point idle quality is starting to lean to the rougher side.