I prefer the 6-bolt crank and I would probably say that later

is better but condition makes at least as much difference as age.

My 122 wagon has a 75 8-bolt block (all I could get at the time)

with about a 70 6-bolt crank and rods (what I had) and it works OK.

The biggest differences are in the heads. My conclusion is that

except for thickness and compression ratio, all B20 E and F heads

are about alike and you can mill the F head to the E compression

ratio. They all have sort of a hump in the intake port that can

be ground down to improve flow somewhat with loss of turbulence.

I don't recommend polishing and have never felt the need for double

valve springs even though I am frequently a lead-footed driver.

I rarely float my valves with standard springs and retainers.

I'm using an IPD 7001 cam which I really like. I use IPD lifters

which are really OEM Chevrolet lifters that require a special pushrod

to be used in the B20. IPD only guarantees their cams if you use

their lifters. In my opinion that is wise because I have had several

cams eaten up by bad OEM Volvo lifters. (Others have had better

results.)

I have used both HS6 and HIF6 carbs and if properly set up they are

fine. (I have even used a pair of HD8 carbs but have since changed

back when I blew up the engine by passing an aircleaner mounting nut

into #2 cylinder. That's why I had to find another block.)I use the

aluminum manifold and FI exhaust manifold. Because of difference in

flange thickness you have to make some half-washers to get the manifold

bolts to tighten correctly. It all looks quite normal when you get

it bolted up. A lot of folks recommend the 75 240 distributor and

electronic ignition system and I would get one if I could find one.