your thinking is right. if you want to compare a 340 with this new stroke, first, you need to know that the 73 piston is exactly 0.100 in. lower than a 68-71 piston (1.740 vs 1.840 compression height) . a 68-71 has the pistons .018 in. above the deck. so a 73 is 1.840 minus 1.740 -.018 = .082 in the hole. using the 3.510 in. stroker crank vs 3.310, the piston is now half the stroke difference minus .082 (3.51-3.31 / 2 -.082) , you get 0.018in., which means the piston ends-up .018 above the deck surface, just like the high comp. 340 but now, it is stroked. it would be a pretty easy to build combo, if you can find pistons for a 73 340, which are not that common nowadays. a 360 piston could be used, although with less compression.
a 318 could very well use this stroke since the compression height is similar to the 73 340 piston. it would be an interesting combo, but the small piston diameter would lead to a 342-343 cid.