[NHRABill]

24mpg might not be too far off for these 4,000lbs+ monsters being pre 1993 it is Tbi injected and I have a friend who is major into these wagons he has 3 and I get to do all the work for him. Don't want to hijack you too much but he gets mid 20's with his custom roadmaster that has the 350 motor that I lowered and modded for him.

you might have issues with your plans. I have his 92 caprice in my driveway right now has the (305 motor) I started taking the trans out today. Some genius replaced the 4l60 that these come with to a 4l60e this made the computer tell the trans to go into full lockup and the speedo to run at 150mph when you were going 10. I picked up a proper non electronic 4l60 for this and will get it installed if it doesn't rain tomorrow or if he didn't modify too much to get the other trans in there. 1993 and up they went to the 4l60E this cars computer is very picky.

If you pitch the computer and all pulled the 4l60 and replaced with a 2wd 700 from a camaro/ firebird from the 80's it should work but from what I read and researched the 4l60 was only a 3 year deal in these cars. There are 3 sensors on these cars all can be seen front he drivers side one on the rear differential one 2 wire back of trans speedo (gear) and a 4 wire plug just behind the linkage. The E model trans switched from a plastic gear speedo to electronic magnetic spark VSS this is what makes it tough. the car is setup even the base 4l60 non E for electronics only reals switch was the speedo gear readout so if you keep your original more I think of it you will have issues.

I hope I am wrong and encourage you to do your homework also I posted a few photos for inspiration these cars can look cool with a little work. This one below is actually a roadmaster funeral home Flower car with a fiberglass hood Impala SS grille flowmaster custom exhaust a very well tuned engine with a few tweaks I made for it. It does average 25mpg according to owner he clocks it when he does his 500+ mile drives every couple months.

My take on it lighten the load these are pigs big weight inside trim down the engine do normal ecomod stuff and clean her up make it look cool. You may even have the baby 4.3 V8 in there yes it came with a tiny 8. Shoot for 30mpg in a monster of a ride that would be cool.