early 351W block wanted for stroker build

halfnelly wrote: '69-'74 351W blocks have more webbing and are stronger, but '69-'70 are a shorter deck height (9.480 vs 9.500) which would impact the parts needed for building a stroker. They're getting harder to come by and really aren't necessary under the 500HP level. '94-'96 blocks are a bit lighter duty but are roller cam ready.

There isn’t a reverse rotation stroker crank out there with wick lines that can be used in an early two piece seal block.   So you are going to be into an 85ish plus casting if youre looking to stay right hand. And you will need to source the one piece rh rotation rear seal.
I haven’t had any trouble breaking old or new blocks.. if you are going to get serious might want to consider a stud girdle on any stock block.    

69 and 70's I believe are the blocks your looking for, although I really doubt you're going to build something where block strength will become an issue.   351's are good for over 500hp with a stock crank more with a forged crank. The Corral has lots of info about where the limits are and what blocks to look for.

Why are you looking for an early block?   Your likely going have a stroker crank that will work with a one piece main seal and has no wick lines, that would be easiest with a later model block.   Depending on what you are planning to do and the quality/availability of the machine shops in your area you may want to consider getting machined bare block from

Ford Strokers

I have used a couple they are well done, although I did have them finish honed after I purchased and measured pistons. Being a marine application and them not knowing what pistons you are using you should discuss ahead of time what exact piston to wall clearance you are going for..