Today, dollar for dollar, is the 318 faster than the 340 ???

We are getting nowhere. So you are saying that on a build the budget is so tight another 2 or 3k will run them out of the hobby? That’s unrealistic. Let the car sit a year and save some money. It’s called delayed gratification. I call it 16 year old thinking. Get it done, cut corners and make it run, rather than consider it an investment.
The more important question is how long do your so called cobble builds last? Mine easily make it 100,000 miles of beating