being the car is a 6cyl car, there are many diffrent things between them and the V8 counterpart.. steering box, rear end, spindles/ brakes.. most conversions don't get things like the V8 steering box, but they should for it to be done correctly..
my suggestion would be to put in another 200/ C4 auto.. it'll be cheapest and easiest, and there pretty decent on gas in good tune ( 20-25 MPG, some can squeeze 30 )... could add a TBI fuel injection using the CFI setup off of a 3.8 from the mid 80's... a 250/C4 would be even better but you would need Granada/ Monarch 250 engine stands for it to sit down in the engine bay correctly...
you could do somthing like a 3.8 V6 from a Thunderbird and that would be neat too.
my suggestion would be to put in another 200/ C4 auto.. it'll be cheapest and easiest, and there pretty decent on gas in good tune ( 20-25 MPG, some can squeeze 30 )... could add a TBI fuel injection using the CFI setup off of a 3.8 from the mid 80's... a 250/C4 would be even better but you would need Granada/ Monarch 250 engine stands for it to sit down in the engine bay correctly...
you could do somthing like a 3.8 V6 from a Thunderbird and that would be neat too.