Block casting number search

There was a transition period in the early days of Chrysler’s return to NASCAR through ARCA racing. Between 89-93 where they were going through the development of a limited run of race team R blocks, then a few hundred over the counter R1 blocks, followed by development of R2 & R3. The MP engine manual I had from around ‘96 covered the different variations in detail. Like you said, “whatever they had around at the time” There were some growing pains in tooling for the new design along with a lot rapid changes going on with development with the new racing programs. Your block was probably cast in the mid ‘92-early ’93 era.