Cletis has a point - I have logged 12,000+ miles on my truck over the last two years - one jaunt across the US and back all on a semi-stock straight axle. I put needle bearing king pins in along with radial tires. With the warmed up 270 it kept up with traffic and had no problems running all day long at 65 - 70 mph on the interstate.
I have designed and built a disk brake kit that bolts to the stock spindles and allows you to run stock rims - add an after market sway bar and you have a great handling truck that looks stock to the uninitiated.
Here is a photo of the mock up in the shop vise.
I have done IFS conversions on trucks with repowering with a V8 - it is a relatively easy deal.
Putting an IFS into a truck and then wanting a 270 - you are going to have to be a good fabricator and know what you are doing - it will be doable, but the level of difficulty goes way up.
Personally - I am happy with the stock straight axle with a couple of minor modifications - drives nice, steering is light and tight and looks stock.
