I am just going to put this out there.....
Everyone I have ever met from the Mopar or GM teams that has "wanted a little more" out of their small block has ended up spending money on the small block, and 3 years later(give or take) yanked the small block and either swapped something more modern or a big block in.
GM people just shrug and drop a 5.3 junkyard engine in or if they want to spend more then $400 they look for a 6.0 or 6.2.
Mopar guys work a bit harder and look for Magnum engines or pull the trigger on a big block.
Mopar, well, a warmed up smog era 400 is going to out-do a 318 handily. Of course, it costs you gasoline lol. but the power bug can bite you hard
And then you will see what people get out of a 400 and the trend will continue....
I would seriously look at what your goals are for the car and decide what is the most effective way to get there before nickle/dime on an engine that 3 years from now you will want to pull out of the car.
I generally find 318's to dissapoint off the line, and then put a big smile on your face once you get to about 35mph and up when they can spin up a bit into their power band.
A big block will lower that MPH requirement
a Magnum small block with an OD transmission bolted to it with some 3.73 rear gears will lower that MPH, and let you keep your gasoline, plus give you a little boost in HP. Much more entailed swap though if you want to keep an OD transmission working for you, most "cheap" ones will need a computer+ harness to go with them. But, if you are going to go that route, might as well move up to a 5.9 also. They will end up costing the same for the project. FB market will have one within 25 miles of your home probably sitting on a tire for under 500 bucks. Or a whole ram truck for 700 so you can take all the harness stuff too. They are kinda everywhere.