I need to replace my L67... Threw a rod yesterday. I found a used 4.6L Northstar out of an 05 GXP. it has 54k miles and comes with the PCM, trans, wiring harness and accessories.

What other mods would be nessesary and what would my performance gains be?

you would loose performance, the SSEi is quicker than the GXP, is more fuel efficient. Replace your L67 They can be had for less than $300 if you look hard enough. where are you located

I'm in central Pennsylvania... I was a little nervouse about buying a used L67 cuz I just trew a rod at 75k miles :( I have only put 2000 miles on the car since i owned it.

Performance depends on what you want and which end of many variables you value.
That said, I havent heard of this swap being done. L67'* are known to be extremely more reliable and long lived than N*'*. I would say someone either beat the **** out of it, or something catastrophic happened down the line ( Like run super hot or out of oil.)

I've seen very few L67s fail like that. And some of us have way more HP then stock. I have shift points between 6000 and 6200 and I'm not worried about hurting anything.

I'd toss another in. Wait..been there did that. But I personally f'd mine up at 186,000. Stupid sober mistake.

N*..uh John, what'* the head gasket/head bolt deal? Wasn't there a possible issue there?

I said "extremely more reliable than a N*" . I wouldnt trade down but I accept the fact it will come apart one day. Hopefully before 70k.

I hope my N* grenades in the next 30k miles, because my warranty will pay for a brand new motor, but chances are it won't, even as hard as I push it. Every time I sit behind that seat and see that red light turn green in a 45 mph zone, there'* this little punk on my left shoulder that says "MASH IT!"

That being said, I average 17 mpg average city/highway, but damn is this thing fun to drive. I'm 23 now, and I doubt I'll be able to have this much fun when I'm 50.

Hopping back on the OP'* topic here. I think it can be done. Morad Parts Company could probably set you up with all the items needed. Most likely that would be an entire cradle and wiring harness drop out. Although no one has done this to our knowledge...a little work and money, I believe anything is possible

Ya, Mallet Ltd. has been dropping N*'* in everything for years. But the services go in the $10-20k range. I see they have moved over to LS1'* for most conversions, including the Solstice. If you have all the hardware and module'*, it should just be a matter of wrenching it all in. It would be a first.