Will my computer from a 03 Blazer run a 366 6.0L from a 3/4 ton 3500?

I was just wondering if a 6.0 can be ran by my oem computer in my 4.3 Vortech 03 chevy blazer LS 2dr 4x4 

I would lean toward NO, but I haven't physically tried it.....I will tell you that both of these trucks have their own security systems which have to be programmed into the PCM.  If it doesn't get the correct fuel continue password from the BCM it will not start the engine, or it will start briefly and die.

Also, the programming for the extra 2 cylinders isn't there...

That, the associated additional wires, and figuring out how to manage the distributorless ignition all make for a fun and expensive endevour...  But I will say this, if someone can take a Series 2 L67 and put it into an '89 Bonneville SSE as I've seen it done, this should definitely be do-able...  Easy, no, but with enough time and money, it can be done.

Actually, putting the L67 into a bonnie is probably not as hard, as all you need is the wiring harness from the vehicle it came out of...
 
ODBI to ODBII swap is what that one comes down to... It's been done a fair number of times on the W-bodies... Swap a 3.1L or base 3.8 for the L67

why cant you just take the computer from the truck you got the engine from? that will take a load of worries off your hands

Yeah, if you're gonna be pulling an engine from a truck, you want to get as much of the wiring for it as possible...