Aaron Willis of Lithia Toyota

"The old BGB, for cars with the old bolts, calls for a more conventional torque method. Newer year BGBs, for cars that came with new (current) bolts, uses the torque + rotation method.

There were indeed different part numbers; in '87 or '88 Toyota did go to different head bolts. However, they only supply the later style. If you order them today, you'll get the newer style, because that is the only choice that Toyota supplies. You can't buy the early style anymore. If you punch in the part numbers, they automatically supersede to the new part numbers, which are as follows (prices are from LithiaToyotaParts.com):

90910-02120 - $3.24 - Head bolt, intake side (x5 = $16.20)
90910-02121 - $3.21 - Head bolt, exhaust side (x5 = $16.05)
Washers:
90201-10344

If you buy new bolts, use the newer torque method that they call for.

Now, the interesting stuff: Nowhere in the BGB does Toyota state that that these are torque-to-yield bolts! Nor do they dictate that head bolts should be replaced, unless they are out of spec. With those two pieces of evidence, you'll have a very hard time convincing me that specifying a torque + rotation method dictates that the fasteners in question are torque-to-yield. Until someone who knows the difference between fact and rumor can contradict what Toyota says, then no, they are not torque-to-yield.

Now, that said, should you change them every time? Hell yes. They are cheap insurance! For less than $33, you have a full set of brand new head bolts. At that price, is it worth worrying about whether you should have replaced them?"