Brad,
Ouch, too bad. Sorry to see this but for what it's worth it could have been worse.
Yes, it appears as though a main cap bolt failed and the opposing bolt then got ripped out of the block webbing.
You mentioned you have a few more blocks. I see your pistons are SRP 150726s. (4.44" bore) I have a set of 150727's (4.39" bore bore) if you have a std bore block and want to save your future overbores for later.
All the 429/460 blocks are good ones, and any of them will accept your particular rotating assembly. (By the way, mic the pistons after detailing them and check rods for straightness, etc). As 2-bolt cylinder blocks, all the different casting revisions have about the same amount of structural integrity and power handling capability, generally speaking.
(I'm gong to discuss "bolts" and "studs" below, and I use that terminology very specifically...BOLTS and STUDS verbatim. Please read as such.)
I think the OEM main bolts are fine but I would completely understand if you have become weary of them. If you must use a different fastener, then opt for some ARP main bolts. I do not recommend the ARP main studs for these engines as I feel they are incorrectly engineered for the application and are cause for more cap walking than the OEM main bolts.
Having said that, I also think that stronger bolts (such as ARP bolts) are for stronger blocks. I've concluded Ford got this block design balanced out pretty well; I've never before seen or heard of a main bolt breaking and they've been used in engines with hp double that of yours. However...I've also come to the concluson that the form of racing you're in is among the most abusive of all racing and so if you want to strengthen your block then a 4-bolt conversion with OEM main bolts might be your best bet. The addition of the Grade 8 7/16" outer bolts will further distribute the loads that the are normally carried by the std 2-bolt mains. Just stepping up to ARP main bolts (in a 2-bolt block) will transfer a greater, focused load to the block's main webbing more-so than the OEM main bolts (which will absorb more of the shock)...I don't like that approach and that's why I prefer the OEM Grade 8 main bolts over the ARP main bolts in the 2-bolt blocks. My philosophy on this requires a lot of explaining; feel free to call if you want to discuss (way too much to type). The easiest and most cost effective way for most end users to get a 4-bolted block is to start with a D0VE-A block and some offshore billet main caps, such as the Procomp main caps. Don't be afraid of the Procomp main caps, they are solid pieces of billet steel that will be fully machined at your engine shop. Otherwise, Milodon makes 4-bolt caps as well.
If you end up needing another block for some reason (if all your blocks are unusable) then I'll give you one.
LO
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All, in regards to the capabilites of the OEM 429/460 passenger car blocks:
The Ford 429/460 passenger car blocks, on any given year of production, use the exact same block casting for that production year. The D0VE-A block casting was available as both a 2-bolt block and as a 4-bolt block but the 460 engine was not produced with a 4-bolt block, the 4-bolted blocks came on 429 SCJ engines and some 429 PI engines exclusively.
The thicker main webbing of the D0VE-A facilitated the 4-bolt conversion. These days there are special 4-bolt main cap conversion kits that enable 4-bolting standard webbed blocks as well.
I have known 2-bolt standard-webbed 460 blocks to have supported 1500 hp (in fact one of those very blocks is in the shop right now). I do not recommend this practice to others.
I have also known 2-bolt standard-webbed 460 blocks to have supported 3000 hp with nothing more than a 4-bolt main cap conversion and an o-ringed deck surface. I do not recommend this practice to others.
