Oh, I understand that but dropping a roller block in will be virtually undetectable to visual inspection. Except for the valve covers, everything else should bolt right up. I'm pretty sure those TBI motors had EGR so I don't even think they're drilled for the vortec manifold. Later ones, yes. But the early ones should be damn near a "plug and play". Even so, your local machine shop can drill and tap later iron heads for an earlier manifold for sub $100. Should be able to transplant almost all of the original L48 accessories from the manifold up right on to the new block/heads.
Hell, that's an even better idea. Get one that actually has the better vortec heads on it, drill and tap for an earlier manifold. Then you have the equipment (EGR), it's there, it's just not recirculating the exhaust gas. As long as you pass the sniffer, why should they care?
Even if the heads won't pass visual, there's nothing saying he can't just tweak and reuse his old L48 heads, should be 882 castings. Pretty small, but they can probably be opened up enough for a noticeable difference. Plus you have the benefit of the one piece rear main. It's just so much better all the way.
OP, I know you have some restraints you have to work within, budgetary, eco-nazi, all that stuff. I understand, really I do. But as I and virtually everyone here that's done this will tell you. You can go down the road you're thinking about, and it will be more fun for a little while. But the very first time you can't pull away from a Honda Accord (this has happened to me), you'll be thinking of how you can get more power. Believe me, I've thrown that money away. I'm just trying to help you skip forward to the happy ending you want.
