1972scout, for some background on these engines. The "602" and "604" crate engines are circle track "spec" engines. They are factory sealed engines, that is they have "seals" on them so you can't do any internal work on them without breaking the seal. About the only thing you can legally do to them is to change the valve springs and adjust lifters. Anything else internally in the engines you have to take them to an authorized rebuilder, who is required to use original replacement parts, and the engine has to be resealed before you can race it again. If your engine has the seals tampered with or broken you are disqualified. If your engine has any internal parts that are illegal upon an inspection you are disqualified. The engine builders are bonded, and there are punishments/fines for an engine builder that "cheats up" an engine. This is the reason why many teams sell an engine that needs no more than a "freshen". By the time they pay a builder for the GM parts and the labor to refreshen the engine, or even to make a fairly simple repair, and to re-certify/reseal it, it's cheaper for them to sell the engine to somebody who doesn't need a "sealed" engine, and to buy another new engine. Sometimes a racer decides that the "crate class" isn't for him, decides to move up to an unlimited class, or just decides that he can't afford racing, so an engine will go up for sale that doesn't need any repairs. Some of the teams that can afford to have purchased multiple engines, dyno them all, keep the ones that dyno the best and sell the rest. As you can see there are a number of reasons for a "lightly" used engine to be for sale.
The "604" CT350/400HP circle track engine
is based on the GMPP "Fast Burn 385" 350ci/385hp engine. This engine doesn't even hit it's HP peak til 5500 or so rpm, so it is totally out of line with the goals you've stated. The "602" CT350/350 circle track engine
is based on the 350HO 350ci/330HP engine
, but has a circle track oil pan and a high rise aluminum manifold added. The 350/350 and the 350HO dyno charts show HP peaks at over 5000 rpm, and torque curves that don't really "come on" til after 2000 rpm, so with your expressed desire to have a lot of low end torque, these aren't ideal either. These 2 engines are both based on a 1 pc mainseal block with Vortec heads, with a GMPP camshaft. They would work well with a milder cam, as BigRoy pointed out, but either will still cost you considerably more than the other engines considered here. The 350/300 HP engine I recommended from Pace is just a "Universal 350" from Goodwrench with the same cam as these 2 engines, but that still seems to be a cam not really in line with your goals. The 350/285HP engine from Sallee Chevrolet is a "Universal 350" that has the same cam specs you said West Coast Engines/Motorwerks would use. It's closer to stock, I suspect it would still give up a little on the very bottom and gain a little more top, which doesn't seem to be a strong priority with you. You seem to want an engine that you can just drop in rather than build/rebuild one (there's NOTHING wrong with that). It seems like the Goodwrench "Universal 350" would probably be the best choice out of all these, given that you would like to have reliability and a warranty. After the warranty runs out, you'll have a good base to build on, you'll already have the nodular crank and PM rods. If you REALLY want to go for a lot of torque, you might want to consider one of the Goodwrench '87 - '95 truck engines. They're designed for torque with the swirl-port heads and a cam with very mild specs. Here's the webpage from Pace Performance showing the "light duty" 1/2 ton 2 bolt main engine: http://paceperformance.com/i-5134967...-7200-gvw.html
. This link is for a 4 bolt main engine from the over 8600lb GVW engines. http://paceperformance.com/i-5134965...-8600-gvw.html
These engines don't have the provisions for a mechanical fuel pump so you would have to run an electric pump. They have the same short block as Vortec engines, so also would be a good base to build on with a nodular crank and PM rods. You would have to have an intake manifold as the '87 - '95 engines have a different bolt pattern than the older intakes. Overall, I think your best/most economical choice is to use get the "Universal 350". At about $1500 it's not much more, or even less than, a lot of the rebuilt long blocks, and it has all new parts with a good warranty, with dealers for the warranty all over the country. It'll use all the parts you have off your present engine, even your intake manifold.