I plan on doing a 460 in my LSC - one of the guys from bangshift and 460ford has done several in T-Birds and says that some car manifolds will work. D3 I think? Maybe D5... will have to get back to you on that. The headers are stupid high, Hookers are 600.00 and Crites are still close to 400. I paid that for the whole car! I find 429/460's in Craigslist all the time for less than 700. The one I got was 400.00 with c6 attached in running condition. There are dedicated 460 sites that will show you how to get cheap, easy, kitten idle smooth 325/350 hp and probably 500 or so lb ft of torque. I went ahead with a .030 bore on the block but could have gotten away with using D0ve heads for compression bump. 206 factory hp wasn't gonna cut it for me. lol.
I went with forged pistons and bought a chinese ebay turbo to install at some point, 337.50, hx55 ripoff. Pretty big thing. I have to agree, a single turbo on a 460 should get you all the torque you need.
The motor mounts are stupid high also, although I got the stands for 50.00 off of Ebay and have some frame pads from a Falcon that I think will work with it. I'll check the part numbers on this later and get back to you. They were 10.00 a piece.
I'll subframe connect it for sure, but I can't really see that much more in the car that needs mods. The trucks used c6's or E4od's, I'm not sure if the OD will fit, but I'm fairly sure the C6 will fit (tightly) based on everything I've read. Since it's what I have, it's what I'll use.
Good luck with your decision! I think a 351 will need a hood mod? Might as well go bold.

As far as cheap, I don't think I can get a 351 in there any cheaper than a 460. Seriously. The other big expense was the pan / oil pickup. Find one from a E350 with a 460 in it and you're good, or buy one from Ford / Fox conversion for 140 or so.
An aluminum head, aluminum intake, aluminum water pump 460 is not that much heavier than an all iron 351. Both will weigh down the front some...