l dont wanna put another miata engine because the nose of the crankshaft braeks off and l dont wannamess with this again its barely got 100 000 miles thiking of maybe a toyota or something thats actually reliable ive heard about the 5.0 swap but really l just want a fun daily driver, everything else about the car is great but l just dont wanna spend so much time on some engine thats badly designed l just fixed it a couple weeks ago and it seems its coming back, so any replacement alternatives?
ps konw about the 5.0 ford but looking for japanese alternatives toyota honda etc

You know there are two Miata 1.6 B6 engines right. One with a short nose and one with a long nose crank? Besides, most B6 is that have failed have been replaced or repaired by now and it may not happen again. Anyway, the reason for the crank nose to snap off is usually a problem during timing belt replacement or replacement of the keyway. The B6 is a great engine, look for another one for your miata

If the key is put back in the engine right there is no problem. There r 8 ways that the key can go in but only one is right.
l would suggest that the easiest swap would be to go to the 1.8. But having bought a Miata with this problem, l elected to go to a newer crankshaft. The ''Large Snout'' crankshaft in specific. The ''Long Nose'' is easier as it does not require a different oil pump. l did the work myself at about the cost of 500 US dollars. l wish l would have had the time to get the replacement crankshaft matched to new bearings ( l just used standard size & it seems to be working OK three years later)
A fun swap is to get the complete set up from a Australian Capri that is turbo charged, swap oil pans (and pick ups), use the cam sensor from the Miata & drop the turbo set up in.
Sources for engines r KIA, some Escorts & other Mazda engines. However many of these require an oil pan & pick up tube swap. l hesitate to use these as l do not know if they have a piston sprayer installed (like the Miata) or just use the squirter hole in the crankshaft & rod area.
If u make sure that the key is put in right & it should work. But any engine will fail when it is not put back together right, & the early Miata engines suffered from shade tree repair shop work ( l can do it my self & who needs a book).

Swap it with the Honda S2000 Engine. Or the Toyota Celica

If you're dealing with a car with a short crank problem, you've got an early 1990 year model. The car is almost 20 years old. Why bother with an expensive engine swap? Have u taken it to a reliable mazda shop that knows about the short crank problem & had them diagnose it? It may be something else altogether.

As for a swap, for a car that old & of that little value, l truely think ur best bet is to find another 1.6 engine out of a 91-92 miata & throw it in.no mods done for the 1.8, & it is a great engine. l know people who have done the 1.8 swap & r still chasing small issues, several years later. A straight swap to another 1.6 is easy, cheap, & will be reliable.