[Yerboogieman]

I refreshed the original 350 in my K10. Nothing too crazy, top end, cam, oil pump, etc. Bottom end was gone through not long ago and some junk refurb heads slapped on. Now that it breathes, I put the carb on it to get it moving, got it on the dyno and tuned it. I swapped in a 700R4 that was built to the hilt with an Advance Adapters spacer. I calculated I think 9:1 compression with the heads and pistons so it will run great on regular 87 octane. Pulls a decent combined 13mpg. I plan on doing fuel injection in the future because carbs are just a controlled fuel leak in my opinion, but for now it is very street friendly.

Advance adapters makes a ton of stuff to adapt to the NP205, like the spacer I used for my 700R4. You can remove the speedo housing from the 205, drill out the speedo cable hole, thread it, and replace the speedo gear with a reluctor ring. They make kits for that. A quick search shows OffroadDesign has a speedo housing kit that is already drilled, threaded and ready to go.

An LS is cool, but I would prefer one in a street car over a truck where weight isn't a big issue. A fully dressed 5.3 iron block is around 100lbs lighter than a fully dressed Gen1 SBC. The reason I kept the 350 in mine was it was numbers matching, 4 bolt main, and aftermarket parts and bolt ons are CHEAP. I spent around $1000 for cam, heads, roller rockers, used intake, used carb, and all the refresh parts. I'm not concerned with numbers matching, just thought it was cool.

I plan to LS swap my BMW E39 when the M54 wears out, except M54s never die.

Basically, if your 383 is already set, healthy and just needs FI and modernized parts, I'd go with that. If it's worn out and probably needs to be blueprinted, I'd swap in the 5.3. Either way, you're gonna need to do an electric fuel pump, maybe lines, and wiring.