I have been studying and trying to experiment with as many different combinations in conjunction with a friend of mine as possible the last couple years as I have an all aluminum big inch engine build in the works right now too. So I thought I might share a little of what I have learned.
There are both stroker cranks and de-stroker cranks already out on the market and have been for quite some time that fit this application. Several different brands in both forged and billet options.
The stock 5.4 stroke is 4.165" which utilizes a 6.658" rod which gives it a 1.60:1 rod to stroke ratio and nets 330Ci.
The most popular stroker combination consists of a 4.415" stroke which utilizes the stock 6.658" rod thus giving it a more negative 1.51:1 rod ratio. However, I have seen strokers of this combination torn apart after extensive use (1 over 800+hp of drag racing two seasons) and with the proper maintenance did not show any increased signs of wear. The one was a drag race only engine and did to have any street duty or high mileage though. This results in an approximate 351Ci with near standard bore size and 380Ci with a 3.7" bore size.
The newer and becoming more popular stroker setup consists of a 4.350 stroke which utilizes the stock 6.900" rod (iirc off the top of my head) thus giving it a more similar to stock 1.59:1 rod ratio. These will net you approximately 345Ci in a near standard bore while giving you 374Ci with the larger 3.7 bore.
The most common destroker at this time utlilzes a 3.75" (4.6 stroker) crank, but is usually only used when in combination with the larger 3.7 bore netting 323Ci. This is used on some well known drag race setups on some 10.5 cars.
The negative effect on the rod ratio is what scares most people out of stroking the already long stroked 5.4l based engine. And the effect it will have on your rpm range. Not only this, but cost always comes in to play as well. With a different stroke comes a complete new build basically as you'll need different pistons, new rods (even if stock size you want to upgrade to forged or billet h-beam/i-beam), bearings, and new timing components (never a good idea to reuse those on a build of this nature IMO) all new blue printing, machining, and balancing, etc. The cranks alone can range from about $700 to upwards of $3000.
Another nice choice is going with a big bore stock stroke 5.4. This is almost the perfect combination IMO. I have helped build a handful of these and they are nice. They have the added cubic inches without the negative effect on the rod ratio and rpm range. The spin up fast and can really make some great power. With the 3.7" bore and stock 4.165" it nets you 358Ci.
Hope that helps share some info with you guys. FFS