no replacement for displacement
 

Hi folks. I have a 1994 Miata, bought new. At 146k miles on it, I decided to get it converted to an Italia by Simpson Design, in 2009. When all the body finish work was done, I started looking into a supercharger. But on the way to the place to do a fit check because the hood line is lower on the Italia. I didn't make it. The radiator cap broke in heavy traffic and I fried the engine before I could get off.
So I decided to bore and stroke it to 2.1L, still with the supercharger. That engine lasted 500 miles. Got a new engine, again bored and stroked and supercharged. That one lasted 1800 miles. Looks like the failure was detonation, even though the A/F ratio was continually monitored and always rich if under power.
So, back I come to naturally aspired, with a V8 this time. My first question is Ford vs. Chevy. Aside from the obvious displacement difference, what are the pros and cons of the different V8 conversions?

Mostly comes down to old school -vs- new design and your performance goal as well as budget.
Since you are in California there is also the emissions situation for your state.

Before making a decision you need to research the California emission requirements for your year Miata and what conversions that limits you to unless 1994 is old enough that the whole problem goes away. Honestly that feels to me like the biggest hurdle as it limits you on engine choices and exhaust system and all the other secondary systems that go along with the drivetrain package.

Once you get those things narrowed down it will determine your realistic drivetrain choices so that options beyond that can be discussed.

Presuming you get the California green light you also might want to consider V6 power.
The LFX V6 engines from newer Camaro's appears to be a good modern reliable way to get 300 HP.

For any swap option you need to know if you intend to do the swap yourself or if you will be having it professionally done.
Mostly that will determine your budget amount as having somebody do the swap will bump the price by quite a bit.

To get an idea of what it takes you might check YouTube for Miata engine swap video's.
Turbo Tom does a high quality LS swap that shows the upper end of how to do it yourself on a car he calls Thunderbolt.
Taylor Ray does a low dollar swap that shows how to do the swap in your garage with used parts and some fabrication skills.

Step 1: Move from California.
Step 2: Install powertrain of choice and enjoy lower taxes.

LOL!

Ischirm4, welcome to the board!

I'v been a Ford guy for many decades. Big and small, bored and stroked. Wonderfull engines that made good reliable power and ;lasted forever.

But then the LS motors hit the streets. They are cheap, light weight, compact, have good displacement, and handle forced induction well. They last just about forever, too.

3 years ago I bought a used 2001 aluminum LS6 with 49K miles; complete from pan to intake, water pump to tail shaft. Including drive shaft, wiring harness, ECU, and some other stuff for $3,500 shipped to my door. I refreshed a couple things, added a couple of things, left the rotating assembly alone, and dropped it in to my race car. It puts over 400hp to the rear tires. I have been racing it since then, won three championships, and it's still going strong. I have certainly gotten my money's worth out if it.

In short, I think you should just drop in a LS1/6 and be done with it.