Which year is the best for the heavier cast block? Want to repower an 86 Grand Wagoneer (Diesel Dazzler II) Dazzler I had a Toroflow 482 V6 in 1980 that got 29 mpg. Want to improve mileage.

As far as used blocks go, in order of my preference the 599, 929, 141.... 506 LAST. The 599 block is said to be the strongest, I believe I saw one for sale in the 6.5/6.2 marketplace not long ago :)

Years... I believe the 599 blocks were in the 1993-1994 trucks.

I highly doubt that you can get much better than 20mpg with a 6.5 turbo. 6.5n/a maybe 25+.

Unless you get some headers made for it ;)

Go with a good 660 6.2 and some tall gears, that should get you about 30.

I highly doubt that you can get much better than 20mpg with a 6.5 turbo. 6.5n/a maybe 25+.

Weight and gearing my friend. Could have 5.88 gears and have mileage worse than a garbage truck. But put a set of 3.08's in there and she'll def get AT LEAST 30 if you ask me.

also, the 6.5 N/A is less efficent specifically because it lacks a turbo.