IFrames are still one of best ways to embed a webpage into another webpage. I have heard that search engines have the capabilities of even following the links on the embedded web pages successfully.
If you want an example of how to use it, look at the following page.
The code used is as follows.
<p><center><iframe src="http://loancalculators.in/calculators/interest-only/interest-only-loan-calculator.htm" frameborder="0" scrolling="no" width="600" height="470"></iframe></center></p>