An interesting 2-stroke diesel is the Junkers Jumo, intended for aircraft service. It was a straight six, opposed piston arrangement with 12 pistons and two crankshafts. Induction air was by blower. The Napier company in England followed up with their Deltic engine, consisting of three banks of six cylinders arranged as a triangle in cross-section, with 18 cylinders, 36 pistons, and three cranks, one at each corner of the triangle. Junkers made a similar engine in the form of a square, with a crank at each corner, 24 cylinders, 48 pistons, and four cranks. Fairbanks Morse made an engine for locomotive service based on this opposed-piston concept also. There is some interesting reading about these on the 'net.
No it can't be done, converted. Build a new block, new heads, then use a sbc crank? That wouldn't make it a sbc.
I've got a Mercury V6 two-stroke in my boat. It's an all-out racing engine from the factory, sold with no warranty and an expected service life of 100 hours. It does make a ton of power, revs like a sum*****, and the complete engine with middle section and lower unit weighs under 400 lbs. The power head by itself is under 200 lbs. This motor has huge ports for intake and exhaust cut into the cylinders. Three-deuces feed a plenum with reed valves and then right into the crankcase. Oil ratio is 25:1, very very fat -- nowadays many 2-strokes run at 100:1. The ports are so large that the piston rings would fall into the holes. So a strip of metal runs north to south in the cylinders at the center of the ports so the rings have something to ride on. You guessed it: this thing is called a Bridgeport.
The V-8 2 stroke was produced by OMC not Mercury, from around 1986 till 1992 or so. It was first produced as power for the F-1 circle boats then a production version was built. The production version shared nothing with the race version except bore spacing. The racer was intoduced around 1984, it had 8 deuces for induction which was later replaced with fuel injection. The racer originally displaced 3500cc and the first productin engine was 3600cc and later was bored to 4 liters. I have an early race powerhead which I have mated to a shortened stock exhaust housing and lower unit. In there day they were the unbeatable in F-1 racing. Two strokes love nitrous and I have a fogger set up on mine but if you don't use discression major damage will occur, I can attest to this.