Just throwing out options. Not doing either one anytime soon but I have Always wanted a 408 but the radix would be a much easier install. I can install the motor myself so that isn't a problem. Just wanting something with some decent power and stock driveablity. May even think about a cammed 6.0. How would gas mileage be on a mild 408.

 

keep in mind he shifts at 6400 vs my 5800

 

Don't put your credit card up yet. That 408 is just a short block. Don't sell that 5.3 either, you'll need lots of donor parts off of it.

You'll need to add:
heads
valve springs
cam
front cover
rear cover
valve covers
valley cover
oil pan
pickup tube
windage tray
gaskets all the way around
bolts all the way around
timing chain set
oil pump
lifters
lifter cups
pushrods
rockers

Plus:
tune
injectors
fuel pump

Quite a few of the above items will need to be new or at least upgraded aftermarket items. The Radix will end up cheaper.

 

LS1 > Radix'd 5.3

This is a tough call for me...I want to say 408, but gas mileage and driveability might suffer. Either way you go, be sure to look into upgrading the tranny (shift kit, servos, converter) and getting an Eaton/Auburn posi if you don't already have one.

If it were me, I'd go 408, but that's only because I would get a big nasty cam to go with it.

 

again radix is awesome man like everybody says you cant beat it for reliability but my vote goes to the 408

 

Damn that's a good point. I guess the Radix is lookin' better and better for what he's looking for.

 

The rotating assembly / short block is the cheap part. Trust me on this Plus, as Richard points out, you'll definately want aftermarket heads, cam, tune, injectors, pump, pushrods (get a hardened set), gaskets, bolts, and the stock parts. All that definately loots your 5.3 and will still end up costing you another $3500 - 4000.

The real question is your goals. If you want a 'mild' 408 for the coolness factor, it is a very expensive option and a radix is just as cool. If you want modest to wow hp (500 or less), and are on a budget, I think radix is the answer. If you want monster hp (like 600+) down the road, then I think the 408 is the answer.

 

actually i changed my mind too you should do both

 

i'd go with the 408. use your 5.3 heads and have the larger intake valves installed to go with new springs, retainers, etc.. from there just go with a mild cam and buy some injectors. the rest of the items are good to have, but from there you'll have a truck just as drivable as one with a radix, but with alot more room for the future. whether you have a radix or 408 you're going to want to do your own tuning or have it done which would equall out. if you treat it as a straight forward engine swap you'll keep cost down, if you just keep adding as you go the radix will be the better deal.

 

There's a reason all the shops I was talking to about a 408 came around to the same amount...between $8,000 and $10,000....because that's what it costs to build a 408. If you have a spare $8,000 laying around with lots of free time, I'd say call some of the vendors on the right and start pricing components. If you have a spare $10,000 and less time, then see if they will build and warranty it. But if all you have is $5K and a weekend, well, you know what the answer is by now...