Cody, don't be mean!
It's a simple process. First, you move the steering rack up to the rad support, because it's in the way of your transmission tunnel. You may have to mount it upside down, to have the shaft pointing the right way. Then, weld a 3/8 drive socket onto the rack, an extension onto the steering shaft, and use craftsman u-joints and extensions to make a steering shaft that'll clear your engine and exhaust and all that. Don't bother tack welding them together, because the welding will wreck the corrosion protection of the tools. Also, check it out. It may steer backwards when your'e done. You'll have to keep that in mind when you're driving.
Once that's out of the way, you need to hack apart the firewall and floor to clear your drivetrain. Lower it with your engine crane so it's hovering there, and then get your metal and welder out, fab up some engine mounts, and weld them in. Just weld them to the sheetmetal.
Then, you just need a transmission crossmember out of a camaro or something. Unbolt it from the donor car, then bolt to your metro's floor in the right spot. Make sure you use big washers!
Then, buy a 4-link kit. And a diff of some sort. It'll likely be WAY too wide, but that's ok. Just use fiberglass or thick rubber to make some sort of fenders so the law doesn't bother you.
Route your exhaust up out the hood for best results. That's the main reason for using a 350 - you just need to flip the manifolds side to side, and they point up! Hooray! Make sure you use those flapper caps like a tractor, or the engine could get filled up with water in the rain, and hydrolock.
The metro gas tank won't work, just strap the gas tank from your doner car down where the spare tire goes with ratchet straps, and run the hoses up to the engine.
I suppose you'll need a shift linkage, throttle linkage, radiator, and stuff. If the front of engine drive belt stuff won't fit, you can always use a jackshaft. Take a look at a toyota previa if you don't know what I mean. It basically bolts to the front of the crank. Then you bolt the crank pulley to it. That way, you can mount the fan and stuff out front. It'll get it out of the engine compartment so you have room to work on the car, and it'll give it a badass mad-max look, to match your rear fender flares.
Then, just weld down some sheetmetal for the transmission tunnel. Lots of guys are gonna say you need to make the unibody stronger to handle the torque of a 350, but the suzuki unibody is actually really tough. My car has almost 100 horsepower, and it's fine. If you're using an 80s carbureted 350, you'll only be making about 120 horsepower, so no big deal.
All this, including the car, engine, transmission, diff, miscellanious parts, steel, 2000 feet of mig welding rod, fuel tank, wiring, etc, should come to around $5000. About the same price as a late 90s lt1 camaro with a 6 speed that you could just get in and drive. But this way, you'd have an ugly, uncomfortable car. And you'd get to do all that extra work.
The favorite: Red turbo 3 swapped 90 firefly convertible with 3 tech cam and gear running 10psi rolling on 7 spoke GTI rims. Needs paint, a top, and more power, but lots of fun.
Honorable mention: 61 ford falcon money pit, 90 5.0 Lincoln LSC coupe with emotional attachment, supercharged teal 99 F150 for carrying firefly parts, and a black turbo volvo wagon with a dog gate to use every day.