For whatever it's worth I have built and installed 3 different Olds engines in my car. I always wanted more and the next step would have been BBO with fuel injection. Based on the cost and performance results of similar builds I decided to stop fighting 60 year old technology and go LS. With all the the NOS parts on it, my 442 appears factory original but it will never be that low mileage, all original collector car. Doesn't bother me at all and the car is a blast to drive.
This is JMO when it comes to LS swaps. Nothing personal against them, and I'd never stop anyone from chasing their car dreams, it's just that the purist part of me..... I couldn't bring myself to do it. There is no arguing that the LS engines are easy to work on for the most part and the parts are plentiful and if taken care of are a great bang for the buck in itself. But as pointed out, nickel and diming to convert it isn't fun.
Execute a 403 swap if you want to keep it looking stock and you can swap over all your accessories without issue. Granted, it's not going to have LS power and the flat torque curve, but it will fit and you won't have to cut a thing. And you could take it off the computer if you wish. You can make enough power to be happy and still the car can likely keep it all in check with the current suspension. And if you wanted to go back stock (as long as you didn't get rid of the original engine), you can later. Or give it to the next owner should you sell it and let them deal with it. If anyone's ever driven a 403 powered car, they can be a lot of fun. Just sayin'. And if you decide to sell it later, you might get the price you want, but experience has shown me that in general you can sell a factory stock car MUCH faster than a heavily modified one. Why? Bigger potential buyer pool.
An LS swap can lead to great power, but that comes with great responsibility to the rest of the drivetrain and suspension. You'll find yourself starting with better shocks, springs, lowering, tubular A-arms....you'll sink a lot of money into it. Buy a Cutlass Supreme, hack it up and paint it like a 442 and you'll get the same thing. With that extra power, you WILL have to do something with the brakes and handling. You can't not. Nobody I've ever seed with an LS swap has left it at that.
You want an LS with great handling? Buy a 5th or 6th gen Camaro SS or ZL1. I get in the ZL1 and start banging gears, it's a sure blast. But believe it or not, I get just as much happiness out of cruising in the G-bodies with 1/3 the power as I do rowing gears in the ZL1.
Just some thoughts to consider. It all boils down to what you want it to be in the end.