So much misconception.
For starters, here's a nice read on the BP swap:
http://imazda.com/forums/showthread.php?t=733
Now to rebutt your cost guesstimates. From PERSONAL EXPERIENCE.
98b/w pro said:
built motor kit 1500(come on your taking it apart might as well)
You're right about the price on that. Building a motor can get very expensive. I spent $100 on a set of used OEM Miata 10:1 pistons, $150 for a 99 Miata head (needed the cams), $180 for timing gears. $300 for head work, $180 for new rings, bearings, $300 for block work and assembly of the reciprocating assembly. Some other misc things, but some of that is optional. Find an engine locally - $200-300 max, do a valve regrind, and a re-ring for another $300, and you have a solid engine for less than $600-700. No Z5 will be as reliable, and certainly not at this cost.
98b/w pro said:
wiring harness 200-500(they're rare as hell)
Not as rare as you think. I found one locally, but they cut it up trying to get it out and ruined it. Then I found one on car-part.com for $100.
98b/w pro said:
Got mine for $120 from a local dismantler. You know... the place that does all the work for you and sells you the parts at ~dealership cost... also consider that I live in California where everything is uber expensive to begin with.
98b/w pro said:
Remanufactured axles go for $60-$70 each. I bought new axles (no core needed) for $90 each. +$60 if you want to do a G-series tranny and need a half-shaft (used).
98b/w pro said:
exhaust manifold 100(used)-400(mazda)
Came attached to the motor.
98b/w pro said:
intake 100(used)-400(new mazda)
You need the MAF, the top cover and the air hose. The rest of the parts are identical. I got a whole intake set for $50, but it turned out to be for a Z5 (stupid people). Then I got just the top cover and hose for $60 from Mazda
Albany Mazda. Or you can just go CAI like I did:
http://imazda.com/forums/showthread.php?t=3
98b/w pro said:
Only one mount is needed if you have a 5spd. In my case that mount came attached to the engine. $60 from Mazda, or a set of Mazdaspeed mounts for about $200 from your favorite importer.
FS engines? No. This is a 2nd gen. Why bother? The BP has a ton of potential with stock internals.