Check the intake; should be casting # 3462848, part # 3462847.
The spreadbore intakes are pretty obvious.
The AVS2 650 fits perfectly on a stock intake.
I've used a stock 440 AVS on stock '68-'69 383 intakes before with no problems.
But yeah, if you're installing a carb with larger venturis/butterflies, you may need a short spacer or open the intake accordingly.