I’ve yet to find an affordable method that I like for transporting Road Bicycles in the back of a pickup truck. I don’t want to remove the front wheel or permanently attach something to the bed and I certainly don’t want to spend hundreds of dollars. Here’s what I came up with:
We bought these silly cheap rear-stay bicycle stands a while ago for roughly $20 apiece. We wanted them to stand our bikes on while stored in our house and for light maintenance and easy chain cleaning. We got ours at Harbor Freight and they are very similar to these that I found on Amazon: Bike Stands
They are very easy to assemble and are extremely lightweight. They are also adjustable, which is important.
The idea is very simple; put the stands in the back of the truck, put the bikes on the stands, tie the bikes down.

Here's a good shot of how I secure my Trek 520 in the back of my pickup truck. Note that my new and improved preferred method is to put the stand on the inside of the bike, not how it is shown here on the outside.

Now, here’s the part that you tuned in for-  what I learned about loading the bikes this way from experience.
I have tried loading the bikes forward and backward and with the rear tires against the cab (backwards) seemed to work the best for my particular bed style with the tie downs in the floor at the front of the bed. I also found that the bikes were more stable with the stands to the inside of the bikes, counteracting the outside pull of the bungee cord. Another thing I found was that it worked much better with the stand adjusted lower so that the back tire touches. Both of these adjustments add more lateral stability. Speaking of, that is the most difficult thing to achieve, lateral stability. In other words, keeping the bikes upright when going around a corner. You will need to experiment with your particular tie-down method. I usually test my ever-changing/evolving method by giving the truck a good side-to-side shake after I’ve tied the bikes down.
I usually tie the bikes down at the rear from the rack to the bed tie-down in the floor and the secure the bikes tightly between each other, again using the rear racks. At the front I do roughly the same thing using the front racks. Sometimes I bungee through the front rims.

View of bikes tied down front and back and between each other. Again, this is my old method with the stands on the outside.

If you don’t have racks, you can bungee to the frame. You’ll want to be careful about scratches though. You may need to create some position specific pads. I’ve created pads in the past using scrap pieces of carpet, cut to fit the position. They were held in place with velcro strips that I ran through slits that I cut in the carpet, kinda like a belt loop. (link to carpet pad post)
(NOTE: Keep in mind that these stands hold your bike by the frame and may indeed cause some scuffing)

Here is a pic with the stands on the inside with the bikes loaded forward

Notice there is no good way to securely lock your bike to prevent theft. We sometimes run a cable lock through the two bikes to prevent the Crime of Opportunity and I have messed with the idea of a cable run through the bed tie-down. No matter what, it’s still just a cable. We always try to practice the 1-of-3 rule; Always keep one of three items on your bike, your butt, your eyes or your lock.

Here is another interesting style of stand that I have never seen before: New Floor Stand. The only problem I see is that it looks like it’s for more of a fat-tire bike. The best Ebay search term I have used was “bicycle floor stand.” (Ebay is the first place I go to for ANYTHING)

WARNING! Be very careful when loading a skinny-tire road style bike into a rack that holds it by the wheel! If the bike tips over for any reason, including lateral shift, you can easily end up with a catastrophically bent rim. Especially when loaded. This goes also for stationary bike stands like at a park or bike shop. We’d rather lean our bikes against something in any of these situations. Don’t me ask how we learned this 😉
I am constantly trying to improve this method and have also been toying with the idea of building a DIY rack specific to my needs, maybe even out of wood. I have Google searched a lot, to see what others may have DIYed, but again, most of them seem geared to fat-tired bikes. If anyone out there has their own ideas/plans/schemes they are willing to share, please email us!!