i did the research in the internet (google) also another forum called forum.miata.net and i didnt find anything about it. its the same if you ask me if you can use a AM3 socket into an Intel motherboard (computer shit)... And i will answer you politely a complete and reasonable answer...

Really? You couldn't find the 1.8L engines end at 05 and the new generation of 2.0L motors begin at 06?

swapped head
 

Hey guys new to the forums. I have a 1993 Mazda mx3. I was going to do a miata engine swap but I've already got a bp block. I saw the original question about swapping heads on the 1.6 with 1.8 dohc 16v. Im not sure if it was answered prior to me but all I saw was no. I put a 1.8 head on mine and its working great. Look for a 1994 Ford escort GT with the 1.8 4 cylinder in it. Of course you know any head work that will be needed such as timing belt and such will be for the 1.8 ford. Only small issue I have is that when looking at the installed 1.8 head. There is a slight misalignment of the oil passage holes. I called and asked a buddy who works at Mazda and he said it wasn't anything to worry about. I'm running a mix of 1 at 5-30 weight and 3 qts 15-40 weight engine oil. With a significant HP and tq increase with the new head. Hope this helped. I know I'm not the owner of a miata but I thought I would see if that helped at all

stdh.txt

Sound like you put a 1.8 BP head on a 1.8 BP motor? That's totally different from putting a 1.8 BP head on a 1.6 B6 motor where the head is going to be hanging off both ends and none of the head bolts or pistons or spark plugs or oil passages or coolant passages line up with eachother.