The C4-G heads are just standard 352/390 heads but with some port work and bigger valves can be made to run well. As far as trying to ID a 428 in the bone yard you can measure the stroke through one of the spark plug holes. You will need to be able to turn the engine over though so bring a breaker bar. Remove the spark plug and turn the engine to TDC. Insert a length of wood dowel and mark it using a common guide. Then bring it down to BDC and mark again using the same guide. Measure the distance between. The 428 will have a 3.98 (4") stroke and a 390 a 3.78. Other than ripping the head and oil pan off this will give you a basic idea what your dealing with. Standard 428 blocks like the ones found in the tbirds will have a sandscratch "A" on the back of the block. The CJ and SCJ a "C". If the block on ebay has one of these it's a production 428 block. These are a few good sites. www.428cobrajet.org which is the CJ registry. Lots of good ID info with pics. Another good forum is www.fordfe.com Some really sharp guys hang there. I would check those tbirds before buying the block on ebay. You will spend much less and have a complete engine. Buying piece by piece is much more expensive and things are not always as advertised sometimes. Ebay is famous for this so please be carefull. There are lots of guys to help and guide you along the way. Be certain you know what your buying BEFORE money changes hands. If you want an auto tranny check out the C6's in those birds also. I'm not familer with those but if it's there in the car it can probably be had cheap hopefully. Casting numbers will be generic for some blocks also. Read the Steve Christ book and see how many different blocks listed are for a C6ME-A. Quite a few.....G.