RB 383's WERE NOT "wide block Poly engines." RB 383's were exactly what they are termed---they were a 383 CID B type block with the same stroke and high deck as a 413, hence RB for "raised block" 383. They take the same B/RB heads as any other Mopar big block.
Also I DO wish people would stop calling the old "A" 318's also known as a "Polysphere head" as a "wide block."
The only reason the old Poly engines looked wide is the HEADS, the block IN FACT is so similar to an LA that if you had an A and an LA BLOCK sitting side by side, you'd have a little trouble telling them apart. They were, in fact, a small block design.
