I'm thinking of putting a 350 or a 383 crate motor in my 87 caprice classic. it's completely stock rite now except for dual magnaflow exhaust. Whats mod should I need to make sure my car runs good as a daly driver.

I know i'm prolly going to need
- Suspension Work
- Rear End Work
- Tires
- I'm getting my 700r4 tranny rebuilt to handle 500hp/550tq
- Bigger Radiator

But what else should I need what what parts belong in the top catagories.
I want to get 400 hp to the ground

Any advice on products that worked well for you will be appreciated

My car is about ~300HP with a more or less stock LM1 engine. It used to have a 305 in it, so one thing you are most definitely going to want to do is put a larger radiator in it. When I had the 305 radiator in it, the car would puke on the highway in the summer. I am now using a 4-core radiator from a truck with a 454. It's a bit overkill - but the engine never gets more than 20 degrees warmer than the thermostat rating (215), even in the hot Phoenix summer.

If you're going to go for 400HP, you're going to want to swap out your likely to be 7.5" rear axle for an 8.5" unit with 3.08 gears (for economy) or 3.42 (for somewhat better performance and no economy whatsoever). I tried 3.42s in my car and what I found is that the performance was somewhat flat over the 3.08s, but highway MPG dropped from about 22-23 all the way down to 16. To me, that's more important with $3/gal gasoline than the .05 second ET advantage I get with the 3.42s over the 3.08s. Food for thought, anyway. You can find a '94-'96 9C1 axle in some junkyards for less than $200 complete with all brake hardware. This is a disc brake setup. It's a direct, bolt-in swap, although you will need to replace your driveshaft for one that's 1" shorter if you have a 7.5" now. Another thing to keep in mind is wheel bolt circle/pattern - your car now has a 5-on-4.75" pattern, the heavy-duty 9C1 stuff, as well as all '91-up stuff, is 5-on-5", you will have to change your wheels to match if you do this swap.

However, if you decide you want 3.42s on an 8.5", and your 8.5" has something else, I have a set of gears here that you can have if you pay to have them shipped. The ring gear is bolted to an open carrier with no spider or axle gears. I won't separate it so you would have to keep in mind the weight of this for shipping - somewhere in the area of 40 lbs total.

is there a easy way to tell a 8.5 and a 7.5? Im putting a 350 in mine to, which will probably have a about 340HP to it.

Mine is a 87 with a 2.56 open diff. I looked on the SPID label for the code for an 8.5 but it doesnt have it.

is there a easy way to tell a 8.5 and a 7.5? Im putting a 350 in mine to, which will probably have a about 340HP to it.

Mine is a 87 with a 2.56 open diff. I looked on the SPID label for the code for an 8.5 but it doesnt have it.

8.5, if it's even on the RPO list, is G87 where 7.5 is G89. Most do not have this on the list.

The 7.5" has a "rounded-square" shaped diff cover, with two pointy blocks under it to the side, one on each side. The 8.5" has a more elliptical oval shaped diff cover pan, and has squareish blocks under the cover on the housing.

8.5, if it's even on the RPO list, is G87 where 7.5 is G89. Most do not have this on the list.

The 7.5" has a "rounded-square" shaped diff cover, with two pointy blocks under it to the side, one on each side. The 8.5" has a more elliptical oval shaped diff cover pan, and has squareish blocks under the cover on the housing.

wouldnt you know it i got a 7.5

is that fine with a 340hp 355 infront of it?

I live about 30 mins from miami-dade county, finding caprice parts that aren't gone already is about the same odds as winning the lotto.

thanks for the offer but i'm gonna look for 3.08 gears cause gas is nearing 4 $ a gal here.

I live about 30 mins from miami-dade county, finding caprice parts that aren't gone already is about the same odds as winning the lotto.

thanks for the offer but i'm gonna look for 3.08 gears cause gas is nearing 4 $ a gal here.

If you can find the *9C1* disc rear axle, those will already have the 3.08s in them. Not that you ever will, but the '94-'96 Impala SS also has a rear disc setup, but the axle is about 1" wider to compensate for the wheel offset on the 17" alloy wheels, also a lot of these are geared 2.93 instead of 3.08.