[TonyMadrid]

From 1969 to 1973 the deck height was 9.480 and it changed in 1974 to 9.503, a difference of .023". If you use an earlier block you have to be sure to order pistons to match the deck height or you will have insufficient piston to valve clearance or you will need a machinist to cut eyebrow reliefs into the piston tops.

Also castings up to 1974 (D4 casting prefix) tend to have greater material thickness. These earlier blocks are good to use if you are considering converting to four bolt mains. The later castings would probably not be able to withstand the extra strain of the four bolt mains.

Nonetheless, even using the later castings, you can build a 400 or 500 horsepower plus engine.

I have also read that the 289 Hi-Po's and the Mexican 302's had main caps with thick chins.

A few good reference books that I use are:

Ford Windsor, Small Block Performance by Isaac Martin and
How to rebuild Small Block Ford Engines by Tom Monroe. They are both HP Books published by the Berkley Publishing Group.

There is also a book called How to Build Max Performance Ford V-8's on a Budget by George Reid, published by Brooklands Books, Ltd., a British company.

All three books are available online, just do a google or amazon search.

Whether you're planning on building the engine yourself or not, these books are very informative and will give you some great baseline knowledge about the Ford family of engines.