At nauseum..318 intake manifold to 340 or 360.

Yup, there are of course two different gaskets, small port 318 and large port 360.
If you're heads are 340 then you need the large port 360 intake gaskets and the Assault intake port will be the best fit, The Edelbrock that has the boss built in for the ac compressor that I linked has the small 318 size intake ports.
I figure you probably do have 340 heads, he just took his Aluminum intake and four barrel off and put the stock 2 barrel back on the sell it as running.
Dual exhaust is another sign, If it has headers I put $1000 on it has 340 heads.