Not to jump topic, but I had an 03 4Runner, V8 limited in Iowa, and with some Goodyear fortera (SP?) tires it was unstoppable in any weather to be thrown at it. Or stoppable, depending on the amount of ice, ironically if you gave the engine some juice it would drive itself out of a slippery situation.
The rust, I would take it to a powder coat/Non-Skid shop, if there's enough "good" metal to coat, the structural ridgidity should be sound. the powder coat will also protect you from future corrosion concerns. I suspect the corrosion is due to winter road treatments in Canada, similar concerns in Iowa, just not quite as extreme.
V6 vs. V8: V8 every time, I've driven both, and the V8 pulls harder and faster without fail. Toyota ran it starting with the 01 Sequoia in mass production, so by 03-06 all the "major" kinks were sorted out.
In mid 2009, I sold my 03 V8 4Runner for around $15000 american, but that was right on with WWW.KBB.com
Hope this helps a little.