The SBC is a cheap source of horsepower. A factory crate motor can be delivered to your door for about 2K. But what you are getting is 50 year old technology yeilding 52hp per liter versus 88hp per liter with the V6 2.5 Mazda in stock trim. The Mazda uses formula 1 technology from a decade ago with the girdled mains and four valve heads. My thought on the conversion is to put a modern motor in therefore updating the drive train not back dating it to a cast iron lump.
Steve

i like the subaru conversion. the motor is small,light,strong and inexpensively available. i bought a complete engine for $950 and a new shortblock for $1200. im shooting for around 350 hp with a garrett t/3, stainless headers,sds engine management,water to air intercooler........ as for the tranny i have an 84' 915 which was gonna go with a cable shifter but now i think im gonna go with the new wevo stuff. i also got 88' 930 brakes, suspension,and 7's and 9's fuchs. my car is a nice 71' almost rustless arizona car with no frame damage. i drove from miami to arizona to get it and towed it back with my blazer.
ive already spent around 8k and will stop counting when i pass 20k, sound familiar? for me its a hobby not an investment. this car will give me joy when i drive it . i think that if you have the time the money,love what you are doing and plan to keep a car that will give you many years of enjoyment then its worth it. good luck.

Old car, PICS!! please? btw what year and model engine are you talking about? thanks

My 914 started life as a two liter 4 then changed to a 2.4 liter type 4. The 2.4 liter was fun but lasted about 15k miles between overhauls. I installed a 2.7 six with a top end overhaul back in 86 and put 100k miles on it before I sold the engine two years ago. I beat the crap out of that six and It never broke down. It finally started to pull the head studs and it was cheaper to buy a stock Euro 3.2 with DME from a wrecking yard than overhaul the 2.7. Now that I'm older (40) the stock 3.2 is a lot less hassle than the webers. It doesn't sound as good as the 2.7 but it is more fun. The four banger was fun but once you had a six you'll never be satisfied with a four banger. I've had my home made six since 1986 and it was worth every penny.