There is an advantage when utilizing a used (seasoned  ) O.E.M. block, is that being that not only was it actually finished machined, by someone whom actually knew what they were doing and understood who would be holding the bag if unsuccessful, but was done so and then actually put into service (tested); with the brand-new, un-finished block (virgin  ), one 'must' go over.......................EVERYTHING!  Do not assume that as handed to you any effort made is ready for use in any fashion.   

       Scott.

     A "300 Six" is an awfully big (external dimension) engine to try and fit in to a '66 Bronco!   

     But, as I have often said:  "If you drop it from high enough, it'll fit!"   

     Scott.

      FrozenMerc,

      A big +!!   

      Scott.

     So-called "Crate Motors",  based on my observations, experience and exposure to customer outcomes, all I can say is .............................GOOD F#%@ING LUCK!   

     And, I wouldn't make one's purchasing decision based on "the warranty" either, as that often will evaporate the moment you have a problem!   

     Scott.

      For those whom might be interested (and in an attempt to get past the all-knowing participant), there were also examples of these reinforced blocks made and utilized as 352's at the 4.00" bore (390 & 410's @ 4.05" bore) which apparently aren't to common.   

     Back several decades ago, Jim Dove came by our shop and in his wandering about came to a stack of FE blocks with the additional webbing and cross-bolt bosses which we had marked as being 352's, at which point he said he had never seen such a thing; and yet here was a stack of 'em?  He said "you've mismarked these" they're probably not the 4.00" bore of a 352, more than likely a 390 block with a 4.05" bore"; I said no, handed him the calipers, he measured them, and then he said: "well I be ......................,  I want to buy them, all of them!"   

     At this time Jim was heavy into his roundy-round effort, and had been utilizing the reinforced example 4.05" bore blocks, converting them to the cross-bolt caps, but having to sleeve them down to the 4.00" bore (cubic inch rule); he said obviously with these blocks (our 352's) he wouldn't need to incur the cost and labor associated in putting eight sleeves in each block.   

     Scott.

Nice try but no...................

      If it's just that I'm failing to communicate properly I apologize.      But if it's because your failing to understand, and/or perhaps your just not familiar with the subject which I have attempted to bring to light (perhaps not so clearly initially, yep, my bad) and with a closed minded perspective you have chosen to engage another, well then, I surrender, you win!   

      But realize that just because the casting number might be "C4" (and it was my mistake to utilize the simplistic reference of "'64" vs. "C4"), this doesn't necessarily mean that is actually the year in which it was cast.   

      Some battles just aren't worth the effort!   

      Scott.

       

An exhaust push rod had broken the adjusting cup. When I removed the rocker assembly with the broken rocker, I found the ARP stud next to it was slightly bent. By all appearance the adjuster had not backed off and the bent stud next to it still appeared to be holding torque.

     When you experience multiple different but related components surrendering at the same instant such as this, I'd be concerned for possible interference causing things to effectively go solid.   At minimum, I'd perform a leak-down test on that cylinder before reassembly and double check the clearances throughout the valvetrain (including the removal of that spring and rechecking the installed height); before having another go at it.      

     Scott.

      From here, I can't really comment of the the other products, but if you run it hard, perhaps you might want to consider different valve locks?   

      Scott.