I have a Mark IV 454 bored and stroked to a 505. Cast steel crank w/1850 bob weight. What SFI flywheel and SFI bellhousing would I need? I have a 12 inch (really is 11.75") SPEC Stage 3+ clutch disc and SPEC pressure plate I plan on using the mcleod M-800 transmission when it's available.

A 12" flywheel is same as an 11" with bigger holes. Get a standard McLeod or other bellhousing and you should be fine.

Devin

those measurements were for the clutch disc

I was also looking more for part numbers

I know there are these:

McLeod Industries 8630 http://www.summitracing.com/parts/MCL-8630/
McLeod Industries 8640 http://www.summitracing.com/parts/MCL-8640/
McLeod Industries 8650 http://www.summitracing.com/parts/MCL-8650/

I just don't know which one to get based on the combination I intend on using.

And I still have no idea what flywheel to use and if I just bolt it on and go on about my merry way.

There is also a $120.30 difference in the 8630 and 8640 when they have the same overview on summitracing. however they do have the difference up at the top:

8630: Bellhousing, Manual, Steel, Chevy, V8, Each
8640: Bellhousing, Steel, Gold Iridited, Chevy, Big/Small Block to Chevy, Ford, Tremec Transmission, Each

8650 has a different overview and reads differently at the top
Bellhousing, Manual, Steel, Buick, Chevy, Oldsmobile, Pontiac, Each

for example, I was looking at these:

http://www.summitracing.com/parts/HAY-10-235/
http://www.summitracing.com/parts/SUM-700182/
http://www.summitracing.com/parts/RAM-1521/
http://www.summitracing.com/parts/RAM-1421/

I just do not know if it will work with my application as far as external/interal balance, whether or not I can just bolt on without doing anything else to it, etc.

I know....it sounds crazy