If I was to replace my LO3 with an L98 or an LT1 from a Vette, How easy would it be to keep the car emissions legal? What would keeping it legal ential? thanks

 

Really depends where you are as to how they enforce the
laws concerning emissions on your car. But to be sure
why not just install all the emissions equipment that goes on a
L98 or a LT-1 with the motor. None of it will affect the full
throttle performance of your car in a significant way. Removing some devices such as EGR can affect drivability and mileage
in a bad way. It's actually better to have it working because
the rest of the system is designed to take advantage of its beneifits. As far as I know it is illegal in both Canada and all of the US, to operate a car on the street without a working catylictic converter if that car origionally
came with one. {EPA Act} Wether the engine is modified, a swap
or passes the emmisions test without it. Still needs that converter to be legal. That would be all Fbodies 1974 or newer.
Doesn't mean you can't modify/ improve your car, like adding headers or a cam or even a complete motor swap. Just don't turn it into a pig with a crippled computer/fuel injection system thats sort of half working. You'll be better off in the long run to install the whole motor package and get that running ace, and then work from there. My car has a complete motor swap from an
old car from the 60's with no emissions eqipment. The law allows me to do this in Ontario (Drive Clean Act) "Hot Rod clause" and the car passed the required emissions standard by a mile. but it still requires a
cat converter to be legal.
Your province or state may have different regulations and enforcement so like I said it really depends where your are.