Then that is a 365hp engine. Its a decent candiate for supercharging, but that depends on the hours on it. I would not SC it without at least a top end refresh and better head gaskets.

A good cam, intake, carb and exhaust combo will get you about 450-475hp.

Either scenario, you are looking at 5k to get the power to get to 70.

Your best banfg for the buck is to get your prop labbed by BBlades. For $400 or so you can gain 2mph or more.

Upgrade the exhaust valves to inconel or Ferrea super alloy while the heads are off if you are planning to run the supercharger. Good insurance. I am 99.7% sure that the black engines just have standard stainless exhaust valves, and that Merc only put the inconel ones in the blue engines.

I have a gen 4 HO for 4k efi making 500Hp. Add a Once over by Bblades and you are there.
http://www.youtube.com/watch?v=L__3xcJfbjs

I would put blower pistons and high temp rings to the list just keep growing until you spend more than the cost of switching motors.

The "cost" of building or "switching" motors to somebody elses "used" motor is subjective........some people want to build their own instead of buying a complete used motor that someone else has built, history unknown, nothing wrong with that......but who knows what they are buying with a "used" motor.......yes a new motor can cost a lot although as long as it is done correctly and maintained, a new motor should last a while..........IMHO....

exactly!! thats why im banging your x old ladymany times,she was well used and abused

You know as well as I do that it does not matter a bit new or used. They all can have issues, yes even a new rebuilt one. I think what you are trying to convey is warranty is worth the $. I have been down both roads and have had decent luck with the used if you can sort out the junk. Check the video does that sound like a pile? These motors push a 10k lb boat to 90 mph no problem. If the person wanted to spend or could spend 10k I would advise him to avisit a reputable builder.
IMHO!

I would build a 525SC clone. Pull the heads and make sure everything up top looks OK. Replace your intake and exhaust valves and full roller rockers. Put on a 177 Weiand with an 850 Holley. Run 4 lbs of boost and run 2 temp range cooler spark plugs. Install a 120' thermastat. Add a higher flow fuel pump and monitor fuel pressure and boost as a minimum. Then lab finish whatever prop you end up running. I think this will get you close???

In my opinion this is a good place to start. Your 454 Mag has good components. The 8.8 compression is a bit high. The weak link are the intake and exhaust valves and the stock exhaust is only good for 450 PSHP at best.

I know it takes a lot of HP to gain a so