History: When I started the real HP car stuff in 1972 Speed Pro and TRW were the two manufacturers of forged pistons for American engines. That is, if you could get them for your engine. They were reasonably priced. If you couldn't get them for your engine then you went to Arias or Venolia or Forgedtrue and paid a lot more. That was it.
They were strong but heavy, same weight as the cast pistons they replaced. There were guys who earned a living lightening TRW and Speed Pro forged pistons for racers.

Then I was out of the game for a while.

Now, Federal Mogul makes Sealed Power for regular performance, and Speed Pro for the high performance crowd. Ironically. the Speed Pro pistons many times use the old TRW part numbers. But TRW pistons are no more. The pistons are still heavy and stout but now they cost quite a bit more than they used to, counting for inflation.

There has sprung up a crop of aftermarket forged piston makers who for a couple of hundred dollars more make a superior piston, in terms of weight and suitability for much higher performance. They used to be double the old TRWs, but now they aren't so much more cost. They have flexibility in specifications and there are many part numbers for shelf stock pistons. Changes to the pistons can sometimes be done for a few dollars or free, so your pistons will be a lot closer to what you need.

In the case of a 383 which has Speed Pro pistons already installed, if it's for a street engine they are about unbreakable. It's not worth trashing them to spend another $800 on a set of "better" pistons.

As far as the carping on the Speed Pros, most of those come from real racers or people who use their engines hard. The JE, SRP, Wiseco, ProTru, Diamond, Icon, Ross, etc pistons fit their needs better. If one was building a 383 from scratch I'd suggest using one of these, but mainly for compression reasons. You can tailor the CR by making modifications to the pistons that are not available from S-P.

R.