The 413 is dimensionally identical to the 440. This means that the trans is a bolt-on deal, from ANY later bigblock. The typewriter trans is special, and would be a great boon to a Nostalgia-class dragracer. Talk trade to the right people, and you might get exactly what you want, with little cash outlay. As for 413 parts availability, as long as you aren't looking to rebuild the engine, it's dimensionally identical to the 440. Heads, intakes, and other external parts bolt right on. Rebuilding can get dicey, as 413 pistons aren't high-demand items. This is why most raised-deck bigblocks are 440s, now.