Many thanks gents. Car on the way so haven't torn in to it. Being a little proactive/anxious. Will add more info once I've gotten in to it.

Service manual shows disc diameter as: 261 / 283 / 348 - 9.5" / 10" / 10.5"

Again, thank you.

Robert

Thank you Carl, bit pricey but I think this is it

RGM

Many thanks gents. Interesting article supports what youve said. I think the next step is to confirm what flywheel I have.

Chevrolet Flywheels from Hemmings Motor News October, 2011 - Jim O'Clair Finding a flywheel to fit your Chevrolet in the mid-Fifties used to be simple: There were only two possible units from 1942-'53. One flywheel (#3705385) covered all 1937-'53 cars and trucks with a 9 1/8-inch clutch disc and a six-bolt mounting pattern; the other (#3705387) covered all 1942-'53 cars and trucks with a 10-inch clutch disc and nine-bolt pattern. Both used 139-tooth ring gears for the starter. After 1953, Chevrolet changed to 12-volt starters, and the number of teeth on the ring gear was changed, but there are still just a few different flywheels used (excluding Hydra-Matic and Powerglide automatics). Some of these flywheels were used on models from the mid-Fifties up into the Eighties. We have included some of the original casting numbers for easy reference. Flywheel #3704831 1954-'55 cars and trucks with 10-inch clutch Flywheel #373919 1958-'65 trucks with 13-inch clutch Flywheel #3739423 1956-'65 cars and trucks with 10 or 10 1/2-inch clutch and 11 5/8-inch bolt pattern Flywheel #3705409 1955-'62 cars and trucks with 10 1/2-inch clutch and 168-tooth ring gear Flywheels #3789730 and #3705410 1955-'62 cars and trucks with 11-inch clutch and 168-tooth ring gear Flywheels #3758595, 3714463 and 3789733 1955-'71 cars and 1955-'85 Chevy and GMC trucks with 11-inch clutch and 12 5/8-inch bolt pattern and a two-piece rear main seal. (1986 and newer flywheels are different because they used a one-piece rear main seal) 1969-'85 Blazer and Sprint 1966-'72 Chevelle 1966-'81 Corvette 1967-'70 Chevy II and Nova 1967-'74 Camaro and 1977-'81 Camaro (with Warner transmission) 1970-'72 Monte Carlo (except 400-cu.in. two-barrel) 1981 Firebird with 305 Chevy engine Flywheel #3971021 1964-'73 full-size Chevy cars and 1965-'73 trucks with 10- or 10.4-inch clutch and 153-tooth ring gear 1967-'85 Camaro 1964-'77 Chevelle 1965-'79 Chevy II and Nova 1965-'68 Corvette with 327 1978-'81 Malibu 1978-'79 Monte Carlo Also these other GM models with straight six-cylinder, V-6 or 262/305 V-8 Chevy engine: 1973-'75 Apollo 1968-'71 Buick Special 1972-'76 Ventura 1973-'76 Omega 1975-'79 Cutlass 1970-'76 and 1980-'85 Firebird 1965-'72 Tempest 1973-'80 Le Mans 1966-'71 F-85 Flywheels #3703870 and #3729004 Models with 11-inch clutch and 168-tooth ring gear 1969-'74 Blazer/Jimmy 1970-'81 Camaro 1970-'71 Impala 1965-'74 Trucks 1970-'75 Chevelle, Monte Carlo 1977-'78 Corvette (180 and 185hp) 1978-'81 Firebird with 305 engine 1978 El Camino 1971-'79 Nova 1977-'79 Omega and Phoenix with 305 engine Flywheel #3993827 1973-'90 Chevy and GMC Truck w/454 1970-'74 Chevelle and Corvette w/454 1971-'74 El Camino and Sprint w/454 Exceptions to the above listings are these few special flywheels that do not interchange with each other or any of the above: 1970-'71 Impala and Monte Carlo with 400-cu.in. two-barrel flywheel does not interchange with any other two-barrel listing 1967-'89 truck with 292 engine (different from all other six-cylinders) 1969 Corvette with a dual disc clutch Additional part number references are available in Volumes III and IV of the Hollander Interchange Manual or the 1929-'57 Chevrolet Master Parts and Accessories Catalog, available online at The Old Car Manual Project. This article originally appeared in the October, 2011 issue of Hemmings Motor News.