Opinions differ, especially on cams. So, these are my own personal opinions. I have no quarrel with those who have different opinions.
(1) Compression: Some say that the 670 heads tend to increase the chances of detonation. So, when you order your stroker assembly, it might be a good idea to order pistons that will reduce the CR down to no more than 9:1.
(2) Cam: The smallest cam I'd even consider is the Summit 2801. It will have a dead smooth idle, plenty of vacuum, and lots of low rpm torque. But, the power will begin to fall off at somewhere around 5000 rpm or less. If you never plan to pull past 5000 rpm, then the 2801 might be OK for you. But, most Pontiac guys consider the 2801 too small for a 455+ Pontiac engine. A similar, but low lift version of this cam is the Pontiac 068 cam, which was used in the 455HO engines.
The Summit 2802 is considered, by many, a decent 455+ cam. It is probably the cheapest decent 455+ cam available. It'll still have a decent idle & vac, and will make good power to 5000 rpm.
Just above the 2802 is the Crane 283951.
Just above that is the Crower 60243.
Next up might be something like the Howard's 410051-14.
Then, the 041 clone, such as the Melling SPC-8, Comp Cams 51-116-3, & Crower 60919, is still considered a good 455+ street cam. I prefer one of these, used with Rhoads lifters. With the Rhoads lifters, this cam has a decent idle, vac, low end torque, and will pull past 5000 rpm easily.
Some, including at least one well known Pontiac engine builder, like the Lunati Voodoo cams. So, a 268 Voodoo might be a good street cam.
There are obviously bigger cams, and roller cams, available for Pontiac engines. But, if you'll be operating below 5000 rpm, MOST of the time, why buy a cam that will make more power above 5000 rpm, but have a rougher idle, less vac, and less low rpm torque ? In other words, it's better to buy a cam that matches the rpm range you'll be operating in, most of the time. IMO