I have done this thing, it is unfortunate that I realize it is almost (few months) 10 years ago.
B21A with M47 (wire) in a 1959 Amazon.
Please don't judge too harsh, the car is still not on the road tho it drives fine, I need to redo a lot of the "solutions". I just add the pictures as they appear when I go through the album, sorry if confuse.
I answer with many pictures, words hard, best show.
The oilpan is fine, the flat/thin part rests on the... the, the big beam thing. I forget word.
If you look at the image above you can sort of make out that I have cut and hammered the horizontal "beam" in the firewall, where the orange hose goes behind the head.
This I think was due to how far back the engine sits for the oilpan "bulge" to get far enough toward the rear to clear the big bottom beam-thing.
Engine mounts need some work.
While the engine clears fine on the driver/intake side, the original cast exhaust manifold would not.
It hits the metal "flap" that is some kind of reinforcement of the body at the a-arm mountings (I think).
I ground it down (it is on the driver side for the steering) but ended up making my own manifold which is thinner and tighter against the engine. More pictures, I just add them as they are in order.
I also had to replace the generator due to the originals size.
I also used 240 radiator and expansion jar. The car had no good engine, cooling or electrics (6v).
Since I did M47 also had to mate driveshaft parts together.
12v battery from some citroen c1 (I think, maybe) fits turned right (my opinion) in original battery shelf
Driveshaft wiggle is 2 mm I recall, not good, not terrible. I read somewhere 2mm was max, of course managed to land on that after welding. I have not noticed while driving. Made a "driveshaft cage" in case of **** happens.
I really need to address the gearbox mount to the body.
Despite my efforts with the exhaust manifold, I had to cut the manifold studs/screws a little to clear for mounting.
Airfilter is a small but crucial thing, I must have crankcase vent in closed loop for inspection.
I made another solution later, don't recall why now. This looks fine.
I used the hole where the original ignitioncoil goes for the throttle wire.
I also use wire for clutch (240).
I need to redo the clutch pedal mount.
I also need to do better with the throttle, maybe just a stronger spring on the pedal it self.
And I reeeeally need to redo the shifter, I made it all "screwable" (not like that) and used a shifter from a ng Saab 900... yeah.
Found how the airfilter looks now.
Maybe more than you asked for.