I am a professional engine builder I port heads for a living and have build literally hundreds of engines for work and dozens of mopar small block and I’m a mopar guy, the 920 heads on the 318 flow more air than 302s into the cylinders, the larger valves are too shrouded, we end up getting more air through our 318’s with 920’s than 302’s that goes for stock and with bolt ons like headers, street cam, intake and carb. If you’re aiming for over 5-600hp then you’ll want larger valves for forced induction but 450 crank is a very easy number to crack out of a 318. We build a ton of them for all the people buying 318 cars because big block cars are so expensive, 340 cars even. The 302’s are superior on the 340 because that shrouding isn’t bad. But for a street engine with a mild cam, 600-750cfm intake with whatever carb combo you’d like and headers when I port 920s and 302s the same just basic porting even not me referencing my cutaway head shelf to see what material I can remove they have a higher port velocity and his high enough that we measure more air coming through them than any other head made by Chrysler that fits a 318. Unless you go notching the cylinder walls for no shrouding. I’m saying this from experience at work and the fact it’s my job. I came here just to see if anyone had tried running that combo before but I guess I’ll be the first to try and I’ll post about it, I’ve got almost every small block head Chrysler has made lying in storage here so if the closed chambers are a no go then I’ll let y’all know what the smallest chamber I was able to use was. Doing a very budget build with a 450 crank hp minimum and a goal of 500 with only pistons, intake, carb, cam and I make headers for the engines I build at work so I’ll probably make those if I have time if not cheapo pair until I can make nice ones. Budget for the engine is $1500 it shouldn’t be hard at all tbh these things are so overlooked. Budget counts for alternator and pulleys/brackets, like it needs to be ready to drop in the car. I’ve actually done it before but I want to make more power, last one I did this way made 418 at the crank with a $1000 budget.