318 Street/Strip build?

For a streeter with a manual trans;If you get to considering aluminum heads;
for a streeter to make the best use of them requires a pretty high Dcr, which means a tiny total chamber volume, which is something the 318 is not normally capable of with typical aluminum heads. So in compensation for the soft bottom end, an automatic-car would want an unusually hi stall TC for street, and unusually high for a streeter rear gears. But with a A230 3-speed,you don't get the TM from the TC at zero-mph,so you will need even more rear gear. And you will need a wide powerband,to cover the large 1-2 shift split, else the engine will fall off the cam; and that usually points to short-period wide LSA cam,which steals cylinder pressure, making this combo really tricky to pull off.
IMO, you will be waaaay ahead of the game with 3.09low Commando A833, no matter how much you have to pay for it, and small-chamber iron heads, and a very fast rate-of-lift cam.
Your saving grace in this situation is stuffing it into a Lightweight-A.
Yes you can use the aluminums with a low Dcr, but what's the point? Aluminum sucks heat out of the chambers big time, and at the same Dcr, your iron heads, all other things being equal, will likely make more power; and the iron heads will have a stronger bottom-end. The nice thing about aluminums is they suck so much heat out of the chambers, it will be difficult for your teener to get into detonation.If you still consider aluminum, look towards the low end of 50cc, cuz by the time you get it bolted on, and cammed up.............the pressure below 3000rpm, where a manual trans is married to most of the time, is slipping away.

But I really want to talk about gears
The A230 comes in 2 flavors;
the V8-A230 with ratios of 2.55-1.49-1.00, ............... .58-.67 splits
the /6- A230 with ratios of 3.08-1.83-1.00, .................59-.55 splits.
the A833 overdrive box...... 3.09-1.67-1.00-.73od ........54-.60-.xx. which can be had really cheap. as low as $50 at swapmeets
and A833 Commando........ 3.09-1.92-1.40-1.00 ....... .62-.73-.71 tight split box; which usually has to be converted to slip-yoke.
As you can see,
the V8 A230 has reasonable splits, but with the 2.55 low-gear,requires a lotta torque to get moving, or a lotta rear gear.
The od box has a terrible 1-2 split
The Commando splits are the best, and
The A230 slanty is a low-rpm gearset with a short 1-2, and a looooong 2-3. It would be fine on the street if geared to not get into third.
A good target for a street 318 is to hit ~52mph,revved out in second. With a 5200rpm power peak, this might be 5400 rpm. And so with 27" tires the math spits out an overall second gear ratio of ~8.36. This maths out to: 5.60s with the 1.49 ratio; 4.56s with the 1.83ratio; 5.00 with the 1.67 ratio; and 4.30s with the 1.92 ratio.
To stick with the A230(V8) and 1.49 second and 3.91s say, you will hit 75@5400, but just 3740 @52, 4315@60 ; not particularly quick no matter how you shake it. So there's no sense in a streeter having a fire-breathing cam with these gears.
To best use the slant A230 with the 1.83 second gear, you might consider a bit less cam and run 4.30s. The 4.30s will get you an overall 7.87 final drive and 52mph would get you 5100 rpm, and so a power peak of perhaps 4900, about 1.5 cam sizes smaller than for 5200. Probably just as quick to 52 but more torque below 3000.
If you're thinking to pull 60mph at the top of second, that's really a bit far out there for a street-318, but with 4.30s would be;
4780 with the 1.49; 5870 with 1.83; 5350 with 1.67; and 6150 with 1.92 ratio. As you can see, having the right gear at the right time, is all about picking the right box.