Hey,
I encourage you to join the bigblockfox mailing list. There are about 125 or so members now. All of us are working on our own Ford-based big block projects.
The address is:
http://www.egroups.com/group/bigblockfox
Also try:
http://www.bigblockmustangs.com/
You are correct in that the earlier blocks are much better for sustaining higher hp than the newer late-model blocks. What years are the strongest I do not know but some members on the bigblockfox mailing list will know for sure.
If you are going to use D0VE (it's actually a zero) heads -- block strength will not be much of an issue because you won't be making any big hp (700+).
I would HIGHLY advise agaist purchasing a 460-based crate motor from Ford. They come with rather weak rods (although I guess now they offer an Eagle rod option which is nice). The moderator of bigblockfox broke his natrually aspirated "stock" 514 crate motor after only 24 or so passes -- and it was a rod that failed. The 514 crate motor, for reference, makes ~600hp and he ran ~133mph on motor.
I also would very highly advice agaist using the D0VE head. At a bare miniumum you'll want to look into the Cobra Jet cylinder head (the new revised ones). The next step up is the Blue Thunder Cylinder Head. Although TFS has a head on the market now, I really think the Blue Thunder is currently the best bang for the buck out there. TFS is rumored to be designed a *great* big block ford head that might get the nod over the blue thunder soon, however.
I would advise NOT running a C4. A nicely prepped C6 is one choice. Another, often overlooked choice, however, is the TH400 -- yes, a Brand X tranny. The TH400 has the advantages of being lighter and having less rotating mass than the bulky C6. Thus, the TH400 consumes less hp. It's a 3 speed.
Finally, as I hinted at earlier, I HIGHLY reccomend upgrading to at least an eagle rod.
I think that for a novice mechanic, going the 460 route is NOT a piece of cake. Thus, unless you have plans to run 10s or quicker OR you have a strong desire to "be different" you should look at a built 302 or 351. However, if you want to run 10s (or heck, even 9s) on motor and 8s or 7s or whatever with a power adder, then the big block route is for you!
A 5" cowl hood *should* net you enough hood clearance. How you set the motor in the engine bay will be key in determining how much hood clearance you have.
I encourage you to use a motor plate to mount the engine. You can use engine mounts -- but I think the motor plate is a much better way to go. Total Performance, who has extensive experience with 460-based swaps, offers a motor plate package and can assist you with any questions you may have about the swap. Yes, you will need custom headers as well.
I don't know about the T5 or the oil pan. A T5 would live w/ a 460 as long as you didn't attach slicks and drive the snot out of it. Cooling is a BIG issue with doing a 460 swap. I think electric fans (yes, more than one) is a must.
Best of luck to you and I hope to see you post on the mailing list.
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Jeff Kane
1990 LX Mustang Coupe