The Chevy inline engines that began production in the early 1960's with the 194 cubic inch Chevy II engine were thinwall castings with 7 main bearings, and they shared a lot of parts with the V8 engines. The rear of the block accepts the same bell housing as the V8's, also flywheels and clutches interchange, I believe. The engine size increased to 230, then 250, and a somewhat modified medium-duty truck engine, the 292 also became available. The 230 and 250 engines' only difference is the crankshaft and pistons, so a 230 can be rebuilt as a 250 simply by swapping the crankshaft and using a piston with a shorter compression height to offset the longer stroke.
All these engines share the same basic cylinder head and intake/exhaust systems, with the exception of the 194, which has smaller valves and a smaller combustion chamber, I believe. Some 292's use a bigger exhaust pipe diameter and a different bolt pattern on the exhaust flange. All of them will benefit somewhat from dual exhausts, but the advantage is mostly cosmetic and sound-wise, not really measureable on a dyno unless some pretty extensive cylinder head modifications are done in addition to the extra pipe. There is an intake port mod known as a "lump port" modification that removes the restriction formed by a cylinder head bolt passageway that really improves the breathing, but it is complicated and expensive, and is only really effective at high RPM ranges not normally used on the street.
The 230 with its short stroke crankshaft really benefits from a good balancing job and lower rear end gears to allow the engine to run higher RPM's. I'm planning to use one in a fiberglass Excalibur roadster project, with three side-draft Weber carburetors, a high performance cam and valve train, and some cylinder head modifications to allow the engine to run in the 7K+ RPM range when necessary.
Jerry
