1988 was an odd year. Sort of a transition year before the CB's arrived. Your block is an early block. Really the only odd thing about your engine is the one year only crank sprocket along with the required matching pulley. The 1988 2.5 Tall Deck is also another odd one. That uses a unique sprocket and pulley too. Here is a couple pics of the crank sprockets.Just saw this, nice! I looked at my block. casting number is 4343834-2 with a date of 1-8-88 and nothing on it seems to match any other engine at least on the crank snout. It has a 5 bolt crank sprocket with a square tooth belt and the bolt circle is the same as the 1989 up, but the pilot on the sprocket is larger. It was removed from a 1987 LeBaron 4 door sedan and was obviously a replacement engine, originally the block was a gray-green color and it has brass freeze plugs in it. Crank is the forged T2 one and the rod numbers come up as 2.5L turbo rods. When I got it I opened everything up, refreshed it and used ARP rod bolts, main and head studs. Definitely a strong engine.