Hi there, I just joined this site to reply to your post.
I'm in England and have owned a block with the same number as yours for about 25 years.
I bought it along with an unused 69 zl1 block which I now have in my 34 coupe.
Only this week I pulled the steel block out to see what I could do with it.
I couldn't identify it by casting number so I googled the number and your post came up.
What I can confirm is that it's a 4 bolt mains truck block with the taller deck height..it has HI PERF TRUCK PASS cast at the front inside the timing cover.
Mine seems to have a stroker crank in it..it's numbered O-250157 which I haven't yet traced..it also has KIEKHAFER rods
Best rgds
Paul mason