No need for forgiveness.    For me, this thread is mostly about information gathering.  For example, prior to this thread, I was not aware that some 428 blocks cast in late '66/early '67 were cast with the bosses extra material in the web.

My 2 cents on the different block castings in relation to installing cross bolt caps in a nutshell.  While it isn't required (as you have noted) to have a block with the cross bolt bosses to install the caps and benefit from them, for whatever reason those blocks were cast with the bosses and extra material (crows feet) in the webs.  While not necessary by any means, it seems like a better base/foundation to start with if cross bolt caps are being added.  This, of course, assumes availability.  Sometimes you have no choice but to work with what is available.

Hello, just wondering if anyone has ever done a comparison on putting the larger CJ valves in a stock 390 GT head.

I have put larger valves in a set of c4 6090g heads with no other work.  Flow numbers before and after were in essence the same.

Also, this question would probably be better suited for the fe technical forum versus private classifieds forum.

Urgefor,

Do you need the C5 and/or the bosses for a specific reason?

Mostly to make my life a bit easier.  I have a '64 block with the bosses but the project car is a '66. I've fabricated some motor mounts to make it fit but it just "bugs" me a bit. Long story short, I was not aware some C5 blocks were cast like that also.  If I can get a C5 block with bosses and extra material in the webs like the '64 block along with the 4 bolt engine mount pattern, it would be a win/win for me.  I have a couple C6 engines.  To be more precise, one engine (from a country squire) along with a complete drivetrain from a '66 Galaxie that was a real man's car.  4bbl, 4spd, no air, no power brakes and no power steering.   

I'm running with the assumption that early model year blocks would have a better chance to be cast with the bosses.  What I don't know is what would be considered "early"?  September to January?  September to April?

Thank you for the information.  Unfortunately I don't see a path forward using your block that won't be lots and lots of extra $$ whether it is bore and get custom pistons or have it sleeved to fit the .030 over pistons I already have.   

Thanks.  I'll keep that in mind.  Looking for a 390 version since I already have a stroker rotating assembly with .030 over pistons (4.08) and some Billet Speedworks crossbolt main caps.

To elaborate a bit more on Scott's response, more information is needed to effectively answer your question.  Without more info, information provided could easily be incorrect once the build is finalized.