Depends how much power you are wanting to put into your V8 swap. Also need to find out what the gearing off the rear end is too. I had a 8" with 3.00, four lug axles and drum brakes. Nothing about that screams strength, it's more like a nice "cruising" rear end.
Not sure what model year car you have, but in my case, I wanted to upgrade. 8" was too weak, the 9" is too expensive/hard to find. So, I went with an 8.8". Took me awhile to find one, but the '79-'93 mustang/thunderbird had the exact same width at my '70. Only thing that needs modification is to weld on spring perches. I bought a housing of eBay for $150 and will buy a 31 spline 5 lug 3.73 kit from American muscle here shortly.
Long story short, if you plan to crank out 350-400 HP with your car, the 8" just may not be durable enough to last much abuse.
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