new engine, what can I reuse from old engine

Well, is the 347 28oz. balance or 50oz. balance? I wouldn't use a used oil pump, a new Melling isn't that much. What cfm is the carb? 500? 600? I think the motor will have a hard time breathing thru the restrictive intake. The chain and gears should be good. Is the oil pan an original or aftermarket? Either way it should be fine. Are the valve covers the stock ones? If so, then you may have a clearance problem and need taller covers. If you've already used the rockers with the covers you have, then you should be fine. The flywheel/clutch/pressure plate should be fine if you have the 28oz balance, if you're using 50oz., you'll have to change the flywheel. The balancer should be fine if the motor is a 28oz. balance motor.

Does all that make sense?

Reuse the timing cover and fuel pump eccentric.

It is a roller block, you will need to plug the dipstick hole in the side of the block. Better yet, ask the engine builder to tap and plug it for you.

If you use a big cam , you may be stretching the limits of a 600cfm carb. AFRs flow really really well. Don't choke them at the carb or intake.

I agree with 1320stang in regards to the performer intake. At a minimum, look at the RPM series. If you go with a victor series, you will definitely need a new carb.

Also check with the engine builder if they recommend a standard or high-volume oil pump. If the bearing tolerances are tight, you will be fine with a standard pump. If looser bearing clearances are used, you may need a high-volume pump to make sure bearing surfaces are lubricated properly. If you go with a high-volume pan, you may want to also consider a larger pan. http://www.streetortrack.com/ has the best prices on Canton pans i've found on the web.

Definitely get a moly pump driveshaft! As an added precaution, I always safety wire the bolts on the oil-pump. The last two engines I have disassembled (factory 5.0 and aftermarket rebuilt 289) had a bolt from the bottom of the oil pump sitting in the pan! This explained the low oil pressure in both engines.

Roller lifters require tall valve covers (free from AFR - good luck).