I am going to buy an Engine oil cooler for my K30 and am a bit confused about what one to get. Its a BB 454 I am looking at Derale part numbers 15503 and 15502 at Jegs. 15503 says GM app. SB BB (Thermostatic) and 15502 is the same just non thermostatic, 15502 doesn't say GM app. thats what confused me. Do I need or want one with a thermostat or one without. Anyone who can help me with choosing an engine oil cooler would be a great help. Thanks