Clearly if he is going to be stroking the 351 and going all out, then the crappy rods in the the 5.4 wouldnt be a concern anyway. He will most likely swap them for somethign else. The romeo 5.4 blocks cant take 1300hp with proper prep. There is a guy locally building a TT 5.4 DOHC navi engine, with most of the parts being bought from here http://sullivanperformance.com
Sean hyland motorsports also has an alluminum 5.4 block, wich would save on some weights(I know, doesnt matter to you). The stock 351 blocks are good to around 600hp, and with high revs, the will split down the middle. Your only option for a high powered/high revs 351 based engine is to buy an aftermarket block such as the dart block. Be expected to put another $1000 on top of the $2k price tag of the block into machine work since they are not a finished block.
The 5.4 DOHC navi engines are probably your best bet for HUGE power without having to get a new block. Both versions of the modular engine blocks are strong, but the romeo is a bit stronger than the windsor. a 4.6 DOHC engine would be more than enough, but hard to come by and would cost quite a bit. Now, from what ive been told, navi(DOHC 5.4) engines are pretty easy to come by, and cost around $5k COMPLETE. throw another $5k at it, and you have one hell of a beast there.