If I had a C/10 truck with an OEM 230, I would be inclined to bump it up to a 250. The block is the same size outwardly. While for Inliners, the Chevy 292 is the Big Block of the L6 world, upgunning to a 292 requires a rare 292-only passenger side motor mount, and accessory brackets like AC and P/S get hard to come by. [My '68 C/10 Stepside came with a production L25, 292 L6, so I'm biased.]
Board Member, Twisted6, Larry Page was president of the Daytona chapter of Inliners International. He might have a line on Florida area rebuilders. You could try a PM.
Some sources:
www.12bolt.com
www.cliffordperformance.com
www.inliners.org
Does anybody have recent experience with an O'Reilly 250 L6 Reman?
What's their quality level gotten to currently?
What kind of warranty does it have?