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'Best' is a term that incites flamewars. I'll explain your options...
There are basically two families of common 8V heads, and two types of each. The common heads in the US are stamped with a casting ID # of 160, 398 or 530 (under exhaust ports #3 & #4.) These are the 'small' heads, and the differences between them are pretty much negligible. Everybody else in the world got some other head options. These castings are numbered 405 or 531. These heads have a slightly larger combustion chamber and a better flowing intake port design (often called a swan-neck port.) The intake port flows better, but the exhaust port is still pretty much the same. The other major variations amongst the heads involves the cooling passage size. Big Cooling Passage (BCP) heads have thinner walls, and may be more prone to detonation damage in a turbo motor. Small Cooling Passage (SCP) heads are a bit stiffer and can take more abuse. Both head types have been run in 14-sec 1/4mile cars, however.
Other minor points - some heads are set up for K-Jet injectors (mounted in head), others for LH (mounted in manifild), but holes can be plugged or blanks can be drilled depending on needs. Turbo heads should have Stellite-coated, sodium-filled exhaust valves, to deal with the extra heat. Again, not necessary, but a nice feature nonetheless.
BTW, when I say that we didn't get the 405 or 531 heads, that's not entirely true. We just didn't get them on the auto engines. Volvo Penta boat motors did feature these heads, and yes, you can swap on right on.
When you start talking about the 'best' head, you get into some heated discussions. There is no doubt that the 405 and 531 heads flow better, and make more power when bolted onto an otherwise identical engine. However, the intake flow on even the small heads already far exceeds the exhaust flow - so improving the intake flow isn't really where the attention should be focused. Some exhaust port work on either head style is where some improvements can be made.
Bottom line, unless you're planning on some more serious modifications, just find a 160 head set up for your stock injection system. If you're going to do some work, I'd spring for a 405 or 531 if you can.
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Speed Racer, '83 240 R, '74 164 E, '93 940 OL1 (Manchester, CT)
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